Input device, input/output device, and data processing device

ABSTRACT

A novel input device that is highly convenient or reliable is provided. A novel input/output device that is highly convenient or reliable is provided. A semiconductor device is provided. The present inventors have reached an idea of a structure including a plurality of conductive films configured to be capacitively coupled to an approaching object, a driver circuit that selects a conductive film from a plurality of conductive films in a predetermined order, and a sensor circuit having a function of supplying a search signal and a sensing signal.

TECHNICAL FIELD

One embodiment of the present invention relates to an input device, aninput/output device, a touch sensor, a display device with an inputfunction, an input device with a display function, a display device, ora semiconductor device.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. Furthermore, one embodimentof the present invention relates to a process, a machine, manufacture,or a composition of matter. Specifically, examples of the technicalfield of one embodiment of the present invention disclosed in thisspecification include a semiconductor device, a display device, alight-emitting device, a power storage device, a memory device, a methodfor driving any of them, and a method for manufacturing any of them.

BACKGROUND ART

Touch sensing circuits in which circuit elements, such as touch signallines (e.g., as drive lines and sense lines) and grounding regions, indisplay pixel stackups are grouped together, and which sense a touch onor near the display are known (Patent Document 1 and Patent Document 2).

A technique in which a common electrode that is for display and arrangedfor each liquid crystal display element is also used as one electrode(drive electrode) of a pair of touch sensor electrodes, and the otherelectrode (detection electrode for a sensor) is newly formed is known(Patent Document 3).

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2011-197685

[Patent Document 2] United States Patent Application Publication No.2012/0218199

[Patent Document 3] Japanese Published Patent Application No.2009-244958

DISCLOSURE OF INVENTION

An object of one embodiment of the present invention is to provide anovel input device that is highly convenient or reliable. Another objectis to provide a novel input/output device that is highly convenient orreliable. Another object is to provide a novel data processing devicethat is highly convenient or reliable. Another object is to provide anovel input device having a display function that is highly convenientor reliable. Another object is to provide a novel input device with highsensitivity. Another object is to provide an input device or the likethat is highly reliable. Another object is to provide an input device orthe like with less contact failure. Another object is to provide aninput device or the like with a small circuit size. Another object is toprovide an input device or the like capable of sensing multiple touches.Another object is to provide a novel input device, a novel input/outputdevice, a novel display device, a novel display device having an inputfunction, a novel input device having a display function, a novel dataprocessing device, or a novel semiconductor device.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the descriptions of the specification, thedrawings, the claims, and the like.

(1) One embodiment of the present invention is an input device includinga first conductive film, a second conductive film, a first signal line,and a second signal line.

The second conductive film has a region that does not overlap with thefirst conductive film.

The first signal line is electrically connected to the first conductivefilm, and the second signal line is electrically connected to the secondconductive film.

The first conductive film is configured to be capacitively coupled to anapproaching object, and the second conductive film is configured to becapacitively coupled to an approaching object.

(2) Another embodiment of the present invention is the input devicedescribed in (1) which includes a driver circuit and a sensor circuit.

The sensor circuit is electrically connected to the driver circuit.

The driver circuit is configured to select the first signal line or thesecond signal line.

The driver circuit is configured to electrically connect the firstsignal line to the sensor circuit in a period during which the firstsignal line is selected. The driver circuit is configured toelectrically connect the second signal line to the sensor circuit in aperiod during which the second signal line is selected.

The sensor circuit is configured to supply a search signal.

The first signal line is configured to receive the search signal.

The first signal line is configured to supply a potential or a currentthat is changed in accordance with a capacitance coupled to the firstconductive film and the search signal.

The sensor circuit is configured to supply a sensing signal based on thepotential or the current.

The above-mentioned input device of one embodiment of the presentinvention includes a plurality of conductive films configured to becapacitively coupled to an approaching object, a driver circuit thatselects one from the plurality of conductive films in a predeterminedorder, and a sensor circuit configured to supply a search signal and asensing signal. Thus, the object approaching the conductive film can besensed on the basis of a potential that is changed in accordance withthe search signal and the capacitance coupled to the conductive film.Consequently, a novel input device that is highly convenient or reliablecan be provided.

(3) Another embodiment of the present invention is an input/outputdevice including a display device and the above-described input device.

The input device is configured to sense an object approaching a displaysurface side of the display device.

The display device includes a first pixel that has a region overlappingwith the first conductive film.

The display device includes a second pixel that has a region overlappingwith the second conductive film.

The first pixel includes a first display element. The second pixelincludes a second display element.

The input/output device described in (3) includes a display device, aplurality of conductive films configured to be capacitively coupled toan object approaching a display surface side of the display device, adriver circuit that selects one from the plurality of conductive filmsin a predetermined order, and a sensor circuit configured to supply asearch signal and a sensing signal. Thus, the object approaching thedisplay surface side of the display device can be sensed on the basis ofa potential that is changed in accordance with the search signal and thecapacitance coupled to the conductive film. Consequently, a novelinput/output device that is highly convenient or reliable can beprovided.

(4) Another embodiment of the present invention is the input/outputdevice described in (3) further including a wiring.

The wiring is configured to supply a predetermined potential. The drivercircuit is configured to electrically connect the second signal line tothe wiring in the period during which the first signal line is selected.The driver circuit is configured to electrically connect the firstsignal line to the wiring in the period during which the second signalline is selected.

The first display element includes a first pixel electrode and a layercontaining a liquid crystal material. The first pixel electrode isdisposed such that an electric field that controls orientation of theliquid crystal material is formed between the first conductive film andthe first pixel electrode.

The second display element includes a second pixel electrode and thelayer containing a liquid crystal material. The second pixel electrodeis disposed such that an electric field that controls orientation of theliquid crystal material is formed between the second conductive film andthe second pixel electrode.

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device including a liquid crystal element,a plurality of conductive films configured to control the orientation ofthe liquid crystal material and be capacitively coupled to an objectapproaching a display surface side of the display device, a sensorcircuit configured to supply a search signal and a sensing signal, and adriver circuit configured to select one from the plurality of conductivefilms in a predetermined order and be electrically connected to thesensor circuit or a wiring. Thus, pixels can be rewritten in apredetermined order, and the object approaching the display surface sideof the display device including a liquid crystal element can be sensedon the basis of a potential that is changed in accordance with thesearch signal and the capacitance coupled to the conductive film.Consequently, a novel input/output device that is highly convenient orreliable can be provided.

(5) Another embodiment of the present invention is the input devicedescribed in (1) further including a driver circuit and a sensorcircuit.

The sensor circuit is electrically connected to the driver circuit.

The second conductive film is disposed such that an electric field thatis shielded by an approaching object is formed between the firstconductive film and the second conductive film.

The driver circuit is configured to select the first signal line and thesecond signal line.

The driver circuit is configured to electrically connect the firstsignal line and the second signal line to the sensor circuit in a periodduring which the first signal line and the second signal line areselected.

The sensor circuit is configured to supply a search signal.

The first signal line is configured to receive the search signal.

The second signal line is configured to supply a potential that ischanged in accordance with the search signal and the electric fieldformed between the first conductive film and the second conductive film.

The sensor circuit is configured to supply a sensing signal based on thepotential.

The above-mentioned input device of one embodiment of the presentinvention includes one conductive film and another conductive filmbetween which an electric field is formed, a driver circuit that selectsthese conductive films in a predetermined order, and a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film. Thus, the object approaching the conductive film can besensed on the basis of a potential that is changed in accordance with anelectric field that is blocked between the plurality of conductive filmsand the search signal. Consequently, a novel input device that is highlyconvenient or reliable can be provided.

(6) Another embodiment of the present invention is an input/outputdevice including a display device and the above-described input device.

The input device is configured to sense an object approaching a displaysurface side of the display device.

The display device includes a first pixel that has a region overlappingwith the first conductive film.

The display device includes a second pixel that has a region overlappingwith the second conductive film.

The first pixel includes a first display element. The second pixelincludes a second display element.

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device, one conductive film configured tobe capacitively coupled to an object approaching a display surface sideof the display device, another conductive film that form an electricfield with the one conductive film, a driver circuit that selects theseconductive films in a predetermined order, and a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film. Thus, the object approaching the display surface sideof the display device can be sensed on the basis of a potential that ischanged in accordance with an electric field that is blocked between theplurality of conductive films and the search signal. Consequently, anovel input/output device that is highly convenient or reliable can beprovided.

(7) Another embodiment of the present invention is the input/outputdevice described in (6) further including a wiring.

The wiring is configured to supply a predetermined potential.

In the period during which the first signal line and the second signalline are selected, the driver circuit is configured to electricallyconnect another signal line to the wiring. The driver circuit isconfigured to electrically connect the first signal line and the secondsignal line to the wiring in a period during which another signal lineis selected.

The first display element includes a first pixel electrode and a layercontaining a liquid crystal material. The first pixel electrode isdisposed such that an electric field that controls orientation of theliquid crystal material is formed between the first conductive film andthe first pixel electrode.

The second display element includes a second pixel electrode and thelayer containing a liquid crystal material. The second pixel electrodeis disposed such that an electric field that controls orientation of theliquid crystal material is formed between the second conductive film andthe second pixel electrode.

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device including a liquid crystal element,one conductive film configured to control the orientation of the liquidcrystal material and be capacitively coupled to an object approaching adisplay surface side of the display device, another conductive film thatforms an electric field with the one conductive film, a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film, and a driver circuit configured to select the oneconductive film and the other conductive film in a predetermined orderand be electrically connected to the sensor circuit or a wiring. Thus,pixels can be rewritten in a predetermined order, and the objectapproaching the display surface side of the display device including aliquid crystal element can be sensed on the basis of a potential that ischanged in accordance with the search signal and the capacitance coupledto the conductive film. Consequently, a novel input/output device thatis highly convenient or reliable can be provided.

(8) Another embodiment of the present invention is a data processingdevice including an arithmetic device and the above-mentionedinput/output device described in any of (3), (4), (6), and (7).

The arithmetic device is configured to receive positional data andsupply image data and control data. The arithmetic device is configuredto determine the moving speed of a pointer in accordance with thepositional data. The arithmetic device is configured to determine thecontrast or brightness of image data in accordance with the moving speedof the pointer.

With this structure, eyestrain on a user caused when the displayposition of image data is moved can be reduced, that is, eye-friendlydisplay can be achieved. As a result, a novel data processing devicethat is highly convenient or reliable can be provided.

(9) Another embodiment of the present invention is the data processingdevice described in (8) further including an input portion. The inputportion includes at least one of a keyboard, a hardware button, apointing device, a touch sensor, an illuminance sensor, an imagingdevice, an audio input device, a viewpoint input device, and a posturedetection device.

Thus, the positional data of the object approaching the conductive filmcan be supplied on the basis of a potential that is changed inaccordance with the search signal and the capacitance coupled to theconductive film. Consequently, a novel data processing device that ishighly convenient or reliable can be provided.

Although the block diagram attached to this specification showscomponents classified by their functions in independent blocks, it isdifficult to classify actual components according to their functionscompletely and it is possible for one component to have a plurality offunctions.

In this specification, the terms “source” and “drain” of a transistorinterchange with each other depending on the polarity of the transistoror the levels of potentials applied to the terminals. In general, in ann-channel transistor, a terminal to which a lower potential is appliedis called source, and a terminal to which a higher potential is appliedis called drain. In a p-channel transistor, a terminal to which a lowerpotential is applied is called a drain, and a terminal to which a higherpotential is applied is called a source. In this specification, althoughconnection relation of the transistor is described assuming that thesource and the drain are fixed for convenience in some cases, actually,the names of the source and the drain interchange with each otherdepending on the relation of the potentials.

Note that in this specification, the term “source” of a transistor meansa source region that is part of a semiconductor film functioning as anactive layer or a source electrode connected to the semiconductor film.Similarly, the term “drain” of a transistor means a drain region that ispart of the semiconductor film or a drain electrode connected to thesemiconductor film. The term “gate” means a gate electrode.

In this specification, a state in which transistors are connected toeach other in series means, for example, a state in which only one of asource and a drain of a first transistor is connected to only one of asource and a drain of a second transistor. In addition, a state in whichtransistors are connected in parallel means a state in which one of asource and a drain of a first transistor is connected to one of a sourceand a drain of a second transistor and the other of the source and thedrain of the first transistor is connected to the other of the sourceand the drain of the second transistor.

In this specification, the term “connection” means electrical connectionand corresponds to a state where current, voltage, or a potential can besupplied or transmitted. Accordingly, connection means not only directconnection but also indirect connection through a circuit element suchas a wiring, a resistor, a diode, or a transistor so that current,voltage, or a potential or can be supplied or transmitted.

In this specification, even when different components are connected toeach other in a circuit diagram, there is actually a case where oneconductive film has functions of a plurality of components such as acase where part of a wiring serves as an electrode. The term“connection” also means such a case where one conductive film hasfunctions of a plurality of components.

Furthermore, in this specification, one of a first electrode and asecond electrode of a transistor refers to a source electrode and theother refers to a drain electrode.

According to one embodiment of the present invention, a novel inputdevice that is highly convenient or reliable can be provided. Accordingto another embodiment of the present invention, a novel input/outputdevice that is highly convenient or reliable can be provided. Accordingto another embodiment of the present invention, a novel data processingdevice that is highly convenient or reliable can be provided. Accordingto another embodiment of the present invention, a novel input devicehaving a display function that is highly convenient or reliable can beprovided. According to another embodiment of the present invention, anovel input device with high sensitivity or the like can be provided.According to another embodiment of the present invention, an inputdevice or the like that is highly reliable. According to anotherembodiment of the present invention, an input device with less contactfailure can be provided. According to another embodiment of the presentinvention, an input device or the like with a small circuit size can beprovided. According to another embodiment of the present invention, aninput device or the like capable of sensing multiple touches can beprovided. According to another embodiment of the present invention, anovel input device, a novel input/output device, a novel display device,a novel display device having an input function, an novel input devicehaving a display function, a novel data processing device, or a novelsemiconductor device can be provided.

Note that the descriptions of these effects do not preclude theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the effects listed above. Other effects willbe apparent from and can be derived from the descriptions of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C illustrate a structure of an input device of anembodiment.

FIGS. 2A to 2C illustrate arrangement of conductive films in an inputdevice of an embodiment.

FIGS. 3A and 3B illustrate a structure of an input device of anembodiment.

FIGS. 4A to 4C illustrate shapes of conductive films in an input/outputdevice of an embodiment.

FIGS. 5A and 5B illustrate structures of an input device of anembodiment.

FIGS. 6A and 6B illustrate structures of an input device of anembodiment.

FIG. 7 illustrates a structure of an input device of an embodiment.

FIGS. 8A and 8B illustrate structures of an input device of anembodiment.

FIGS. 9A to 9C illustrate structures of a sensor circuit of anembodiment.

FIG. 10 is a timing chart showing a method of driving an input device ofan embodiment.

FIGS. 11A to 11D illustrate a structure of an input/output device of anembodiment.

FIG. 12 illustrates a structure of an input/output device of anembodiment.

FIG. 13 illustrates a structure of an input/output device of anembodiment.

FIGS. 14A to 14C each illustrate a structure of a driver circuit of anembodiment.

FIGS. 15A to 15C illustrate structures of an input device of anembodiment.

FIGS. 16A to 16F illustrate structures of an input device of anembodiment.

FIGS. 17A to 17C illustrate a structure of a pixel of an embodiment.

FIGS. 18A to 18D illustrate structures of an input device of anembodiment.

FIGS. 19A to 19D illustrate a structure of an input device of anembodiment.

FIG. 20 illustrates a structure of a driver circuit of an embodiment.

FIG. 21 illustrates a structure of an input device of an embodiment.

FIG. 22 illustrates a structure of an input device of an embodiment.

FIG. 23 illustrates a structure of an input device of an embodiment.

FIG. 24 illustrates a structure of an input device of an embodiment.

FIGS. 25A to 25C illustrate structures of an input device of anembodiment.

FIGS. 26A1, 26A2, 26B1, and 26B2 illustrate methods of driving aninput/output device of an embodiment.

FIGS. 27A and 27B illustrate a structure of an input/output device of anembodiment.

FIGS. 28A to 28C illustrate a structure of an input/output device of anembodiment.

FIGS. 29A and 29B illustrate a structure of an input/output device of anembodiment.

FIGS. 30A and 30B illustrate a structure of an input/output device of anembodiment.

FIGS. 31A to 31D illustrate structures of an input/output device of anembodiment.

FIGS. 32A and 32B illustrate a structure of an input/output device of anembodiment.

FIGS. 33A to 33D illustrate a structure of a transistor of anembodiment.

FIGS. 34A to 34C illustrate a structure of a transistor of anembodiment.

FIGS. 35A and 35B illustrate a structure of a data processing device ofan embodiment.

FIGS. 36A to 36C illustrate structures of display portions of anembodiment.

FIGS. 37A and 37B are flow charts of programs of an embodiment.

FIG. 38 schematically illustrates image data of an embodiment.

FIGS. 39A and 39B illustrate structures of a data processing device anda data processing system of an embodiment.

FIGS. 40A and 40B are flow charts of programs of an embodiment.

FIGS. 41A to 41C are a cross-sectional view and circuit diagramsillustrating structures of a semiconductor device of an embodiment.

FIG. 42 is a block diagram illustrating a structure of a CPU of anembodiment.

FIG. 43 is a circuit diagram illustrating a structure of a flip flopcircuit of an embodiment.

FIGS. 44A to 44H illustrate structures of electronic devices of anembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

An input device of one embodiment of the present invention includes aplurality of conductive films configured to be capacitively coupled toan approaching object, a driver circuit that selects one from theplurality of conductive films in a predetermined order, and a sensorcircuit configured to supply a search signal and a sensing signal.

Thus, the object approaching the conductive film can be sensed on thebasis of a potential that is changed in accordance with the searchsignal and the capacitance coupled to the conductive film. Consequently,a novel input device that is highly convenient or reliable can beprovided.

Hereinafter, embodiments will be described with reference to drawings.Note that the embodiments can be implemented with various modes. It willbe readily appreciated by those skilled in the art that modes anddetails can be changed in various ways without departing from the spiritand scope of the present invention. Therefore, the present inventionshould not be construed as being limited to the following description ofthe embodiments. Note that in structures of the invention describedbelow, the same portions or portions having similar functions aredenoted by the same reference numerals, and descriptions thereof are notrepeated. Furthermore, the same hatching pattern is applied to portionshaving similar functions, and the portions are not especially denoted byreference numerals in some cases.

Note that a content (or part thereof) described in one embodiment can beapplied to, combined with, or replaced with another content (or partthereof) described in the same embodiment and/or a content (or partthereof) described in another embodiment or other embodiments.

Note that in each embodiment, a content described in the embodiment is acontent described with reference to a variety of diagrams or a contentdescribed with a text in this specification.

By combining a diagram (or part thereof) described in one embodimentwith another part of the diagram, a different diagram (or part thereof)described in the embodiment, and/or a diagram (or part thereof)described in another embodiment or other embodiments, much more diagramscan be formed.

Embodiment 1

In this embodiment, structures of an input device of one embodiment ofthe present invention are described with reference to FIGS. 1A to 1C toFIG. 10.

FIGS. 1A to 1C illustrate a structure of an input device 700T of oneembodiment of the present invention. FIG. 1A is an example of a blockdiagram illustrating the structure of the input device 700T of oneembodiment of the present invention. FIG. 1B is an example of a blockdiagram illustrating part of the input device 700T in FIG. 1A in detail.FIG. 1C is an example of a schematic cross section of the input device700T taken along the cutting plane line W1-W2 in FIG. 1B.

FIGS. 2A to 2C are schematic diagrams illustrating a layout ofconductive films in the input device of one embodiment of the presentinvention. FIG. 2A illustrates the conductive films arranged in acircle. FIG. 2B illustrates the conductive films arranged in a curvedline. FIG. 2C illustrates the conductive films arranged in a polygon.

FIGS. 3A and 3B are schematic diagrams each illustrating the inputdevice of one embodiment of the present invention. FIG. 3A schematicallyillustrates a structure of the input device including conductive filmsto which a plurality of signal lines is connected. FIG. 3B schematicallyillustrates a structure of an input device including a plurality ofsensor circuits.

FIGS. 4A to 4C are schematic diagrams illustrating shapes of conductivefilms of the input device of one embodiment of the present invention.FIGS. 4A and 4B schematically illustrate a structure of an input devicein which a plurality of rhombic conductive films is arranged. FIG. 4Cschematically illustrates a shape of a side of each rhombic conductivefilm.

FIGS. 5A and 5B and FIGS. 6A and 6B are schematic diagrams eachillustrating a structure of the input device of one embodiment of thepresent invention which includes two driver circuits. FIG. 5Aschematically illustrates a structure including two driver circuits andtwo sensor circuits. FIG. 5B schematically illustrates a structureincluding two driver circuits and one sensor circuit. FIG. 6Aschematically illustrates a structure including two driver circuits andtwo input regions provided in the lateral direction. FIG. 6Bschematically illustrates a structure including two driver circuits andtwo input regions provided in the vertical direction.

FIG. 7 is a schematic diagram illustrating a structure of the inputdevice of one embodiment of the present invention which includes threedriver circuits and three input regions.

FIGS. 8A and 8B are schematic diagrams illustrating structures of theinput device of one embodiment of the present invention including signallines arranged in different directions. FIG. 8A schematicallyillustrates a structure of an input device including signal linesarranged in different directions and a driver circuit. FIG. 8Bschematically illustrates a structure of an input device includingsignal lines arranged in different directions and two driver circuits.

FIGS. 9A to 9C are circuit diagrams each illustrating a structure of asensor circuit in the input device of one embodiment of the presentinvention.

FIG. 10 is a timing chart showing a method of driving the input deviceof one embodiment of the present invention.

<Structure Example of Input Device>

The input device 700T described in this embodiment includes, forexample, a conductive film C1, a conductive film C2, a signal line ML1,and a signal line ML2 (see FIG. 1B).

Note that the conductive film C1 and the conductive film C2 can beselected from a plurality of conductive films C including a conductivefilm C (g, h) (see FIG. 1A). Furthermore, the signal line ML1 and thesignal line ML2 can be selected from a plurality of signal lines MLincluding a signal line ML (g, h) (see FIG. 1A).

Note that each of g and h represents a variable and an integer of 1 orlarger.

For example, the signal line ML (g, h) is connected to the conductivefilm C (g, h), and a signal line ML (1, 1) is connected to a conductivefilm C (1, 1). That is, numbers in parentheses are used to facilitateunderstanding of connection. Note that the layout of the conductivefilms C can be, for example, a matrix, but the layout is not necessarilya matrix.

Each of the conductive films C1 and C2 represents a conductive filmselected from the plurality of conductive films C. Each of the signalline ML1, the signal line ML2, a signal line ML3, a signal line ML4, asignal line MLS, and a signal line ML6 represents a signal line selectedfrom the plurality of signal lines ML.

As an example, the plurality of conductive films C and the plurality ofsignal lines ML are preferably provided over the same substrate, inwhich case the manufacturing cost can be reduced and connection can befacilitated, for example. Note that one embodiment of the presentinvention is not limited thereto. For example, some of the conductivefilms C may be provided over a substrate and some of the conductivefilms C may be formed over another substrate.

For example, the conductive film C2 and the conductive film C1 have aregion where they do not overlap with each other. For example, aconductive film adjacent to the conductive film C1 can be used as theconductive film C2. Alternatively, a conductive film may be providedbetween the conductive film C1 and the conductive film C2.

For example, the signal line ML1 is electrically connected to theconductive film C1. In addition, the signal line ML2 is electricallyconnected to the conductive film C2 (see FIG. 1B). Note that forexample, in a region of the conductive film C1, a black dot thatoverlaps with the signal line ML1 indicates connection between thesignal line ML1 and the conductive film C1. Similarly, in a region ofthe conductive film C2, a black dot that overlaps with the signal lineML2 indicates connection between the signal line ML2 and the conductivefilm C2.

For example, each of the conductive films C1 and C2 has is configured tobe capacitively coupled to an approaching object (see FIG. 1C). Notethat, the signal line ML1 and the signal line ML2 seem to have differentheights in FIG. 1C, but one embodiment of the present invention is notlimited to this. In the cross-sectional view, the signal line ML1 andthe signal line ML2 may be provided at the same height or differentheights.

Note that capacitance can be formed between the plurality of conductivefilms C (including the conductive films C1 and C2) and an object such asa finger or a pen. Therefore, each of the conductive films C canfunction as one of electrodes of a capacitor (for example, selfcapacitance of the conductive film C1 or self capacitance of theconductive film C2).

Note that capacitance formed between the conductive film C1 and theobject such as a finger or a pen is called self capacitance of theconductive film C1, and capacitance formed between the conductive filmC2 and the object such as a finger or a pen is called self capacitanceof the conductive film C2 in some cases.

The object such as a finger or a pen approaching the conductive film C1functions as the other of the electrodes of the capacitor (for example,the self capacitance of the conductive film C1). Thus, capacitance(i.e., the self capacitance of the conductive film C1) between theconductive film C1 or the like and the object such as a finger or a penvaries.

Alternatively, capacitive coupling may be formed between the pluralityof conductive films C, for example, between the conductive films C1 andC2. In other words, a change in the value of capacitance between theconductive film C1 and the conductive film C2 caused by the approachingobject, such as a finger or a pen, may be sensed. Note that capacitanceformed between the conductive films C1 and C2 is called mutualcapacitance between the conductive films C1 and C2.

Consequently, it can be said that each of the conductive films C isconfigured to serve as an electrode for a touch sensor, for example.

Note that, for example, each of the conductive films C may have afunction of an electrode of a display element (e.g., a common electrode)in addition to a function of an electrode of a touch sensor.Accordingly, each of the conductive films C (e.g., the conductive filmC1, the conductive film C2, or the conductive film C (g, h)) is calledcommon electrode, sensor electrode, capacitance electrode, electrode,first electrode, second electrode, or the like in some cases.

The input device 700T includes, for example, a driver circuit 703 and asensor circuit DC1 (see FIG. 1A). Note that a structure in which theinput device 700T does not include the driver circuit 703, the sensorcircuit DC1, and the like and another device or another module includesthe driver circuit 703, the sensor circuit DC1, and the like may beemployed.

Note that in the case where the plurality of signal lines ML is providedover a substrate different from a substrate provided with the drivercircuit 703, each of the signal lines ML is connected to the drivercircuit 703 through a connection terminal, a wiring, an anisotropicconductive particle, a silver paste, a flexible printed circuit (FPC),or a bump, for example.

In the case where the plurality of signal lines ML is provided over thesubstrate provided with the driver circuit 703, a special connectionportion is not needed. Therefore, in the case where the driver circuit703 and the plurality of conductive films C or the plurality of signallines ML are provided over the same substrate, the possibility ofgeneration of contact failure can be reduced, leading to an improvementin reliability.

As an example, the driver circuit 703 may be formed over the substrateover which the plurality of conductive films C or the plurality ofsignal lines ML is formed. In that case, they can be formed through thesame manufacturing process, which can reduce the manufacturing cost.Note that one embodiment of the present invention is not limited tothese structures.

For example, the sensor circuit DC1 may be formed over a substratedifferent from the substrate over which the plurality of conductivefilms C or the plurality of signal lines ML is formed. Alternatively,the sensor circuit DC1 may be formed over a substrate different from thesubstrate over which the driver circuit 703 is formed.

For example, the sensor circuit DC1 may be formed over a single crystalsilicon substrate or an SOI substrate. Alternatively, the sensor circuitDC1 may be formed over an IC chip. Consequently, with the use oftransistors with high current drive capability and small characteristicvariations, a circuit with high sensing accuracy can be formed. Notethat one embodiment of the present invention is not limited to thisstructure.

For example, the sensor circuit DC1 may be connected to the plurality ofsignal lines ML not through the driver circuit 703. In that case, thenumber of sensor circuits DC1 may be two or more. In addition, thedriver circuit 703 is not necessarily provided.

For example, the driver circuit 703 has a function of selecting at leastone of the plurality of signal lines ML. Alternatively, for example, thedriver circuit 703 has a function of sequentially selecting at least oneof the plurality of signal lines ML. Alternatively, for example, thedriver circuit 703 has a function of selecting at least one of theplurality of signal lines ML in an arbitrary order.

For example, the driver circuit 703 has a function of selecting eitherthe signal line ML1 or the signal line ML2.

For example, the driver circuit 703 has a function of selecting at leastone of the plurality of conductive films C. Specifically, the drivercircuit 703 has a function of selecting, for example, the conductivefilm C1 or the conductive film C2.

For example, the driver circuit 703 has a function of a multiplexer or ademultiplexer.

For example, the driver circuit 703 has a function of letting currentflow between the signal line ML1 and the sensor circuit DC1 in a periodduring which the signal line ML1 is selected.

For example, the driver circuit 703 has a function of letting currentflow between the signal line ML2 and the sensor circuit DC1 in a periodduring which the signal line ML2 is selected.

For example, the driver circuit 703 has a function of preventing currentfrom flowing between the signal line ML1 and the sensor circuit DC1 in aperiod during which the signal line ML1 is not selected. Alternatively,for example, the driver circuit 703 has a function of preventing currentfrom flowing between the signal line ML2 and the sensor circuit DC1 in aperiod during which the signal line ML2 is not selected.

For example, the driver circuit 703 has a function of bringing thesignal line ML1 into a floating state in the period during which thesignal line ML1 is not selected. Alternatively, for example, the drivercircuit 703 has a function of bringing the signal line ML2 into afloating state in the period during which the signal line ML2 is notselected.

For example, the driver circuit 703 has a function of supplying apredetermined voltage (e.g., a constant voltage) to the signal line ML1in the period during which the signal line ML1 is not selected.Alternatively, for example, the driver circuit 703 has a function ofsupplying a predetermined voltage (e.g., a constant voltage) to thesignal line ML2 in the period during which the signal line ML2 is notselected.

For example, in the case where the plurality of signal lines ML isconnected to the sensor circuit DC1 not through the driver circuit 703,each signal line ML needs a circuit for supplying a signal or a circuitfor reading a signal in the sensor circuit DC1. Alternatively, onesensor circuit DC1 needs to be connected to each of the signal lines ML.

The driver circuit 703 has a function of selecting one or more signallines from a plurality of signal lines and a function of switching thesignal lines ML every certain period. For example, the driver circuit703 has a function of selecting only one signal line from the pluralityof signal lines ML in a predetermined order. This structure can reducethe number of circuits for supplying a signal or circuits for reading asignal in the sensor circuit DC1. Specifically, the number of circuitscan be reduced from the number corresponding to the number of signallines ML to one corresponding to the one selected signal line ML.Alternatively, the number of sensor circuits DC1 can be reduced from theplurality of signal lines ML to one corresponding to the one selectedsignal line ML. In other words, the number of circuits in the sensorcircuit DC1 or the scale of the circuit can be reduced by providing thedriver circuit 703. Alternatively, the number of sensor circuits DC1 canbe reduced.

Note that the driver circuit 703 is simply called circuit, firstcircuit, second circuit, or the like in some cases.

The sensor circuit DC1 is electrically connected to the driver circuit703, for example. The sensor circuit DC1 has a function of, for example,supplying a search signal. Here, the search signal refers to, forexample, a signal supplied for sensing to the signal line ML (g, h) orthe conductive film C (g, h).

For example, the sensor circuit DC1 has a function of supplying a squarewave search signal. Alternatively, the sensor circuit DC1 has a functionof supplying or outputting a pulse signal. Alternatively, the sensorcircuit DC1 has a function of supplying or outputting a signal to asensor.

For example, the sensor circuit DC1 has a function of sensing a changein a capacitance value. Alternatively, the sensor circuit DC1 has afunction of detecting a current value. Alternatively, the sensor circuitDC1 has a function of detecting the amount of charge. Alternatively, thesensor circuit DC1 has a function of integrating a signal.Alternatively, the sensor circuit DC1 has a function of convertingcurrent into voltage. Alternatively, the sensor circuit DC1 has afunction of detecting a voltage value. Alternatively, the sensor circuitDC1 has a function of converting an analog signal into a digital signal.

For example, the sensor circuit DC1 has a function of reading a signalfrom the sensor. Accordingly, the sensor circuit DC1 is simply calledcircuit, first circuit, second circuit, or the like.

For example, each of the signal lines ML, such as the signal line ML1,has a function of supplying the search signal or the like to theconductive film C1.

For example, each of the signal lines ML, such as the signal line ML1,has a function of supplying a predetermined voltage, for example, acommon voltage to the conductive film C1. Alternatively, each of thesignal lines ML, such as the signal line ML1, has a function ofreceiving the search signal from the driver circuit 703 or the sensorcircuit DC1.

For example, in order to detect the capacitance coupled to theconductive film C1 (i.e., the self capacitance of the conductive filmC1), the signal line ML1 has a function of supplying a potential changedin accordance with the search signal to the conductive film C1 (see FIG.1C).

For example, in order to detect the capacitance coupled to theconductive film C1 (i.e., the self capacitance of the conductive filmC1), the signal line ML1 has a function of supplying current forcharging and discharging the self capacitance of the conductive film C1to the conductive film C1.

For example, the plurality of signal lines ML have a function ofextracting potential or current of the plurality of conductive films Cto the outside of regions where the conductive films are provided (e.g.,the driver circuit 703 or the sensor circuit DC1).

For example, the plurality of signal lines ML have a function ofelectrically connecting the plurality of conductive films C to theoutside of the regions where the conductive films are provided (e.g.,the driver circuit 703 or the sensor circuit DC1).

For example, the plurality of signal lines ML have a function ofsupplying a signal for a sensor to the plurality of conductive films Cor the like.

For example, the plurality of signal lines ML have a function of readingthe signal for a sensor from the plurality of conductive films C or thelike.

For example, the plurality of signal lines ML may have a function ofsupplying a common voltage to a common electrode of a display element.Accordingly, the signal line ML (e.g., the signal line ML1, the signalline ML2, or the signal line ML (g, h)) is simply called wiring, firstwiring, second wiring, or the like in some cases.

For example, when a user of the input device brings an object such as afinger close to the conductive film C1, the capacitance coupled to theconductive film C1 (i.e., the self capacitance of the conductive filmC1) is changed. For example, the value of the self capacitance of theconductive film C1 is larger when the object such as a finger is closeto the conductive film C1 than when the object is not close to. For thisreason, in the case where the self capacitance of the conductive film C1is charged and discharged, that is, in the case where a pulse signal issupplied to the conductive film C1, the amount of current or chargeneeded for a steady potential state of the conductive film C1 is changeddepending on the self capacitance value. For example, when the objectsuch as a finger is close to the conductive film C1, the selfcapacitance value is large, so that the amount of current or chargeneeded for the steady potential state of the conductive film C1 islarge. Consequently, for example, current flowing through the signalline ML1 is changed by the influence of a finger approaching theconductive film C1.

The sensor circuit DC1 has a function of sensing a sensing signal. Thevalue of the sensing signal is in accordance with the self capacitancevalue of the plurality of conductive films C.

For example, the sensor circuit DC1 can change the potential of thesignal line ML1 in order to sense the self capacitance value. Inaddition, at this time, the sensor circuit DC1 can detect the value ofthe current flowing through the signal line ML1, the integral value ofthe current, the peak value of the current, or the amount of charge. Asa result, the sensor circuit DC1 can detect the amount of change in theself capacitance influenced by the finger approaching the conductivefilm C1. Thus, the sensor circuit DC1 can sense a finger of a user orthe like approaching the conductive film C1. Moreover, the sensorcircuit DC1 can output the sensing result to an external circuit.

In particular, in the input device 700T of one embodiment of the presentinvention, the conductive films C can be independently controlled. Thatis, to the conductive films C, the respective signal lines ML areconnected. Therefore, the plurality of conductive films C can beindependently controlled by independently controlling the plurality ofsignal lines ML. When two or more objects (e.g., a finger or a pen)approach the input device 700T at the same time, the objects can beindependently detected. Thus, the input device 700T enables amulti-touch function.

The above-mentioned input device 700T of one embodiment of the presentinvention includes a plurality of conductive films configured to becapacitively coupled to an approaching object, a driver circuit thatselects one from the plurality of conductive films in a predeterminedorder, and a sensor circuit configured to supply a search signal and asensing signal. Thus, the object approaching the conductive film can besensed on the basis of a potential that is changed in accordance withthe search signal and the capacitance coupled to the conductive film.Consequently, a novel input device that is highly convenient or reliablecan be provided.

Note that the input device 700T can be used in, for example, aself-capacitance touch panel.

The input device 700T can include the plurality of conductive films Carranged in a line, a straight line, a curved line, a circle, a polygon,or a matrix, for example. Specifically, as an example of arrangement ina matrix, q conductive films C in the row direction and p conductivefilms C in the column direction that intersects the row direction can bearranged (see FIG. 1A).

Note that g is a variable and an integer greater than or equal to 1 andless than or equal to p. Similarly, h is a variable and an integergreater than or equal to 1 and less than or equal to q. In addition, prepresents the number of conductive films C in the vertical direction,and q represents the number of conductive films C in the horizontaldirection. Therefore, each of p and q is an integer greater than orequal to 1.

For example, in the case where the conductive films C are arranged in amatrix of p rows and q columns, p conductive films C are arranged in thevertical direction and q conductive films C are arranged in thehorizontal direction; thus, p×q conductive films C are disposed intotal. That is, here, p represents the number of conductive films Carranged in the vertical direction and q represents the number ofconductive films C arranged in the horizontal direction.

Note that a conductive film selected from the plurality of conductivefilms C can be used as the conductive film C1, and another conductivefilm selected from the plurality of conductive films C can be used asthe conductive film C2.

Instead of the arrangement in a matrix, FIG. 2A shows an example ofarrangement in a circle, and FIG. 2B shows an example of arrangement ina curved line, and FIG. 2C shows an example of arrangement in a polygon.

The input device 700T includes the signal line ML (g, h) electricallyconnected to the conductive film C (g, h) (see FIG. 1B). Here, in thecase where one signal line ML is connected to the conductive film C (g,h), the reference numeral of the signal line ML is also (g, h). Forexample, a wiring extends in the row direction or a wiring extends inthe column direction can be used as the signal line ML (g, h). Forexample, the signal line ML (1, 1) is connected to the conductive film C(1, 1), and a signal line ML (p, q) is connected to a conductive film C(p, q). For example, in the case where the conductive films C arearranged in a matrix of p rows and q columns, p×q signal lines ML aredisposed in total.

Specifically, for example, in the case where 405 conductive films C arearranged in total in a matrix of 27 rows and 15 columns, 405 signallines ML are used in total in the input device 700T.

The driver circuit 703 has, for example, a function of selecting onesignal line ML from the plurality of signal lines ML in a predeterminedorder. For example, the signal line ML1 is selected from the p×q signallines ML, and then the signal line ML2 is selected.

For example, FIG. 3A shows an example in which a plurality of signallines is connected to one conductive film. Specifically, three signallines ML are connected to one conductive film C. For example, withrespect to the conductive films C arranged in a matrix of 27 rows and 15columns (405 conductive films C in total), 1215 (=405×3) signal lines MLare used in the input device 700T. Note that the number of signal linesconnected to one conductive film is not limited to three. Connecting aplurality of signal lines to one conductive film can reduce wiringresistance. As a result, the sensitivity of a sensor can be improved.Note that the case where a plurality of signal lines which extend in thesame direction is connected to one conductive film is described, but oneembodiment of the present invention is not limited to this.

Note that in FIG. 3A, the signal line ML1, the signal line ML2, and thesignal line ML3 are connected to one another outside the driver circuit703. Similarly, the signal line ML4, the signal line MLS, and the signalline ML6 are connected to one another outside the driver circuit 703.With such a connection, the circuit configuration of the driver circuit703 can be simplified, or the number of output terminals of the drivercircuit 703 can be reduced. Note that one embodiment of the presentinvention is not limited thereto. Each of the signal lines ML1 to ML6may be separately connected to the driver circuit 703.

The input device 700T can include a control line CL, for example. Thecontrol line CL can be electrically connected to the driver circuit 703,and can have a function of supplying a control signal to the drivercircuit 703. For example, a start pulse signal, a clock signal, anenable signal, a pulse width control signal, or the like which controlsthe operation of the driver circuit 703 can be used as the controlsignal.

Note that FIGS. 1A to 1C and the like illustrate an example in which theconductive film C (g, h) has a square shape, but one embodiment of thepresent invention is not limited to this. The conductive film C (g, h)can have a variety of shapes such as a rectangular shape, aparallelogram shape, a rhombic shape, a star shape, a polygonal shape, acircular shape, or an ellipsoidal shape. FIG. 4A illustrates an examplein which the shape of the conductive film C (g, h) is different fromthat in FIGS. 1A to 1C.

In addition, a smooth line such as a straight line or a curved line isillustrated as each side of the conductive film C (g, h), but oneembodiment of the present invention is not limited to this. For example,each side of the conductive film C (g, h) may have a sawtooth shape (azigzag line) as illustrated in FIG. 4C. With such a stepwise shape, aboundary between the conductive films C can conform to a boundarybetween pixels.

Note that FIGS. 1A to 1C and the like illustrate an example in which onedriver circuit 703 is provided, but one embodiment of the presentinvention is not limited to this. For example, the number of drivercircuits 703 may be two or more. In that case, the sensor circuit DC1may be provided for each driver circuit 703. Alternatively, one sensorcircuit DC1 may be provided for the plurality of driver circuits 703.

For example, FIGS. 5A and 5B illustrate the input device in which twodriver circuits are provided. The input device illustrated in FIG. 5Aincludes a driver circuit 703A, a driver circuit 703B, a sensor circuitDC1A electrically connected to the driver circuit 703A, and a sensorcircuit DC1B electrically connected to the driver circuit 703B.

For example, signal lines ML in odd-number rows can be connected to onedriver circuit and signal lines ML in even-number rows can be connectedto the other driver circuit. With such a connection, the driver circuit703 can be divided to the right and left sides, resulting in anefficient layout. Alternatively, the sizes of the driver circuits can besmall by the driver circuit division, which enables a narrower frame.

The input device illustrated in FIG. 5B includes the driver circuit703A, the driver circuit 703B, and the sensor circuit DC1 electricallyconnected to the driver circuit 703A and the driver circuit 703B. Notethat in the case where one sensor circuit DC1 is shared by the pluralityof driver circuits 703, it is necessary to control the operation of eachdriver circuit 703 in order to avoid crosstalk.

Note that a method of extracting the signal lines ML from an inputregion where the plurality of conductive films C is provided is notlimited to the method of extracting the signal lines ML from one side ofthe input region as in FIGS. 1A to 1C. For example, the input region maybe divided into two or more regions and the signal lines ML may beextracted from the regions.

For example, FIG. 6A illustrates an example in which the input region isdivided into a right region and a left region, and a signal line MLA(1, 1) is extracted from a region 775A and a signal line MLB (1, 1) isextracted from a region 775B.

For example, the signal line MLA (1, 1) and the signal line MLB (1, 1)are disconnected near the center of the input region. A conductive filmCA (1, 1) is connected to the signal line MLA (1, 1), and a conductivefilm CB (1, 1) is connected to the signal line MLB (1, 1); thus, theconductive film CA (1, 1) and the conductive film CB (1, 1) can beseparately operated.

Note that in the case where the input region is horizontally long, forexample, the input region is preferably divided into a right region anda left region as illustrated in FIG. 6A; and in the case where the inputregion is vertically long, for example, the input region is preferablydivided into an upper region and a lower region illustrated in FIG. 6B.Thus, the lengths of the signal line MLA and the signal line MLB can beshortened. Consequently, parasitic capacitance or wiring resistance ofthe signal line MLA and the signal line MLB can be reduced, so that thesensitivity of a sensor can be improved.

For example, when the diagonal of the horizontally-long input region isgreater than or equal to 10 inches, more preferably greater than orequal to 14 inches, the input region may be divided into an upper regionand a lower region as illustrated in FIG. 6B; and when the diagonal ofthe vertically-long input region is greater than or equal to 10 inches,more preferably greater than or equal to 14 inches, the input region maybe divided into a right region and a left region as illustrated in FIG.6A. With such a structure, although the total number of signal lines isincreased, parasitic capacitance or wiring resistance for each signalline can be reduced. Consequently, even with a large input region, asensor with high sensitivity can be achieved.

Note that the number of divided input regions is not limited to two, andmay be three or more. FIG. 7 illustrates the case where the input regionis divided into three regions. In that case, the driver circuit 703A,the driver circuit 703B, and a driver circuit 703C may be provided forthe divided input regions. Similarly, the input region may be dividedinto four regions and the signal lines may extracted from four sides.Note that one embodiment of the present invention is not limited to theabove examples.

For example, a plurality of signal lines which extend in differentdirections may be connected to one conductive film as illustrated inFIGS. 8A and 8B. For example, both a signal line that extends in thevertical direction and a signal line that extends in the horizontaldirection may be connected to one conductive film.

For example, as illustrated in FIG. 8A, the conductive film C (1, 1) isconnected to a signal line MLC (1, 1) that extends in the verticaldirection and a signal line MLD (1, 1) that extends in the horizontaldirection. For example, a conductive film C (1, 2) is connected to asignal line MLC (1, 2) that extends in the vertical direction and asignal line MLD (1, 2) that extends in the horizontal direction. Forexample, a conductive film C (2, 1) is connected to a signal line MLC(2, 1) that extends in the vertical direction and a signal line MLD(2, 1) that extends in the horizontal direction.

With such a structure, wiring resistance of the signal lines can bereduced, and thus the sensitivity of a sensor can be improved. Inaddition, even with a large input region, a sensor with high sensitivitycan be achieved.

Furthermore, for example, signal lines ML connected to the sameconductive film may be connected to each other. For example, the signalline MLC (1, 1) and the signal line MLD (1, 1) may be connected to eachother. For example, the signal line MLC (2, 1) and the signal line MLD(2, 1) may be connected to each other. Note that one embodiment of thepresent invention is not limited thereto. For example, the signal lineMLC (1, 1) and the signal line MLD (1, 1) are not necessarily connectedto each other.

For example, as illustrated in FIG. 8B, the driver circuit 703A may bedisposed such that the signal line MLC (1, 1) and the like that extendin the vertical direction are easily connected to the driver circuit703A, and the driver circuit 703B may be disposed such that the signalline MLD (1, 1) and the like that extend in the horizontal direction areeasily connected to the driver circuit 703B. In that case, for example,a signal line MLC that extends in the vertical direction and a signalline MLD that extends in the horizontal direction which are connected tothe same conductive film are preferably selected at the same time.

For example, the signal line MLC (1, 1) and the signal line MLD (1, 1)are selected at the same time. Thus, current flows between theconductive film C (1, 1) and the sensor circuit DC1 via the signal lineMLC (1, 1) and the signal line MLD (1, 1).

For example, the signal line MLC (1, 2) and the signal line MLD (1, 2)are selected at the same time. Thus, current flows between theconductive film C (1, 2) and the sensor circuit DC1 via the signal lineMLC (1, 2) and the signal line MLD (1, 2).

The number of sensor circuits DC1 can be reduced by controlling thedriver circuit 703A and the driver circuit 703B in this manner. Notethat one embodiment of the present invention is not limited thereto. Forexample, depending on circumstance, driving may be performed in such amanner that one of the driver circuit 703A and the driver circuit 703Bis operated and the other is not operated.

Note that the input device 700T of one embodiment of the presentinvention can be disposed over a dedicated substrate or over a surfaceof a counter substrate or a sealing substrate of the display device.Alternatively, the input device 700T can be disposed on a rear surfaceof a protective substrate such as a cover glass substrate.Alternatively, the input device 700T integrated with a display elementor a pixel can be disposed over a TFT substrate, an element substrate,or the like of the display device.

<<Structure Example>>

The input device of one embodiment of the present invention includes theconductive film C1, the conductive film C2, and the signal line ML1 orthe signal line ML2. The input device of one embodiment of the presentinvention can include the conductive film C (g, h) or the signal line ML(g, h). The input device of one embodiment of the present invention caninclude the driver circuit 703, the sensor circuit DC1, or the controlline CL.

<<Conductive film C1, conductive film C2, conductive film C (g, h),signal line ML1, signal line ML2, signal line ML (g, h), control lineCL>>

A conductive material can be used for the conductive film C1, theconductive film C2, the conductive film C (g, h), the signal line ML1,the signal line ML2, the signal line ML (g, h), the control line CL, orthe like.

For example, an inorganic conductive material, an organic conductivematerial, a metal material, or a conductive ceramic material can be usedfor the conductive film C1, the conductive film C2, the conductive filmC (g, h), the signal line ML1, the signal line ML2, the signal line ML(g, h), the control line CL, or the like.

As an example of a material of the conductive film C1, the conductivefilm C2, the conductive film C (g, h), the signal line ML1, the signalline ML2, the signal line ML (g, h), and the control line CL, a metalelement selected from aluminum, gold, platinum, silver, copper,chromium, tantalum, titanium, molybdenum, tungsten, nickel, iron,cobalt, palladium, and manganese is given. Alternatively, an alloycontaining any of the metal elements described above can be used for theconductive film C1, the conductive film C2, the conductive film C (g,h), the signal line ML1, the signal line ML2, the signal line ML (g, h),the control line CL, and the like. In particular, an alloy of copper andmanganese is suitable for microfabrication by a wet etching method.

Note that these conductive films and wirings may have a mesh pattern ora nanowire structure in order to have improved light transmittingproperty. Alternatively, the conductive films or the wiring may containa conductive material having a mesh pattern or a nanowire structure. Inthat case, even when the material itself does not have alight-transmitting property, the material can transmit light because ofhaving many spaces. Accordingly, the films, wirings, or materials havinga mesh pattern or a nanowire structure can increase conductivity and alight-transmitting property.

For example, a single-layer film or a multilayer film can be used.Specifically, a two-layer structure in which a titanium film is stackedover an aluminum film, a two-layer structure in which a titanium film isstacked over a titanium nitride film, a two-layer structure in which atungsten film is stacked over a titanium nitride film, a two-layerstructure in which a tungsten film is stacked over a tantalum nitridefilm or a tungsten nitride film, a three-layer structure in which atitanium film, an aluminum film, and a titanium film are stacked in thisorder, or the like can be used for the conductive film C1, theconductive film C2, the conductive film C (g, h), the signal line ML1,the signal line ML2, the signal line ML (g, h), the control line CL, orthe like.

Note that a light-transmitting material may be used in one embodiment ofthe present invention. For example, a conductive oxide to which indiumoxide, indium tin oxide, indium zinc oxide, zinc oxide, or gallium isadded, such as zinc oxide, can be used for the conductive film C1, theconductive film C2, the conductive film C (g, h), the signal line ML1,the signal line ML2, the signal line ML (g, h), the control line CL, orthe like. In particular, the conductive film C1, the conductive film C2,and the conductive film C (g, h) are preferably formed with any of thesematerials because these conductive films preferably have alight-transmitting property in the case where they are integrated with adisplay device, for example.

Note that a single conductive layer or a multi-layer conductive layerformed with a metal element selected from aluminum, gold, platinum,silver, copper, chromium, tantalum, titanium, molybdenum, tungsten,nickel, iron, cobalt, palladium, and manganese may be formed over orunder the conductive film C1, the conductive film C2, and the conductivefilm C (g, h) to overlap with the conductive films. This structure canreduce the resistance value. In the case where a light-transmittingproperty is needed, these conductive films may be provided only in aregion that does not need a light-transmitting property and not in alight-transmitting region. Thus, both a reduction in resistance valueand a light-transmitting property can be achieved.

For example, a film containing graphene or graphite can be used as theconductive film C1, the conductive film C2, the conductive film C (g,h), the signal line ML1, the signal line ML2, the signal line ML (g, h),the control line CL, or the like.

Specifically, a film containing graphene oxide is formed and is reduced,so that a film containing graphene can be formed. As a reducing method,a method with application of heat, a method using a reducing agent, orthe like can be employed.

For example, a conductive polymer can be used for the conductive filmC1, the conductive film C2, the conductive film C (g, h), the signalline ML1, the signal line ML2, the signal line ML (g, h), the controlline CL, or the like.

<<Driver Circuit 703>>

For example, any of a variety of sequential circuits, such as aselection circuit, a decoder, or a shift register, can be used in thedriver circuit 703. Alternatively, a circuit in which a large number ofswitches are provided and which controls the conduction (on/off) statesof the switches can be used in the driver circuit 703.

Specifically, a shift register that includes a plurality of selectioncircuits and has a function of supplying selection signals, or the likemay be used in the driver circuit 703. Accordingly, one signal line canbe selected from the plurality of signal lines in a predetermined order.

Note that the number of sensor circuits DC1 connected to the drivercircuit 703 may be changed in accordance with the structure of thedriver circuit 703. For example, one sensor circuit DC1 is connected tothe driver circuit 703 in FIG. 1A, but one embodiment of the presentinvention is not limited to this. Two or more sensor circuits DC1 may beconnected to one driver circuit 703. FIG. 3B illustrates an example inwhich a sensor circuit DC11, a sensor circuit DC12, a sensor circuitDC13, and a sensor circuit DC14 are connected to one driver circuit 703.In the case where the plurality of sensor circuits DC1 is connected toone driver circuit 703, the plurality of sensor circuits DC1 can beoperated at the same time, which enables parallel processing andincreases the reading speed of the sensor. Alternatively, the readingtime can be longer, and thus the reading accuracy of the sensor can beincreased.

For example, a transistor can be used in the driver circuit 703 or thesensor circuit DC1.

<<Transistor>>

For example, a bottom-gate transistor or a top-gate transistor can beused in the driver circuit 703.

For example, a transistor including a semiconductor containing anelement belonging to Group 14 can be used. Specifically, a semiconductorcontaining silicon can be used for a semiconductor film. For example,single crystal silicon, polysilicon, microcrystalline silicon, oramorphous silicon can be used for the semiconductor film of thetransistor. In addition, germanium, gallium, arsenic, or the like can beused for the semiconductor film of the transistor.

For example, a transistor including an oxide semiconductor can be used.Specifically, an oxide semiconductor containing indium or an oxidesemiconductor containing indium, gallium, and zinc can be used for asemiconductor film.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used. Specifically, a transistor that uses an oxide semiconductorfor a semiconductor film can be used.

Alternatively, for example, a transistor including a compoundsemiconductor can be used. Specifically, a semiconductor containinggallium arsenide can be used for a semiconductor film.

For example, a transistor including an organic semiconductor can beused. Specifically, an organic semiconductor containing any ofpolyacenes and graphene can be used for the semiconductor film.

<<Sensor Circuit DC1>>

For example, an oscillator circuit, a pulse signal output circuit, acurrent measuring circuit, a peak current measuring circuit, acurrent-voltage converter circuit, an integrating circuit, an ADconverter circuit, or an amplifier circuit can be used for the sensorcircuit DC1.

A current value measurement circuit, a peak current measurement circuit,a current voltage conversion circuit, an integrator circuit, an ADconversion circuit, or the like can be used as the sensor circuit DC1.Thus, whether a finger or a pen approaches a conductive film is sensedfrom a current value, for example. The sensed result can be given to theexternal circuit as a sensing signal.

For example, a pulse signal output circuit or an oscillator circuitcapable of generating a square wave, a sawtooth wave, or a triangularwave can be used as the sensor circuit DC1. Accordingly, a signalgenerated from the sensor circuit DC1 can be used as the search signal.

The sensor circuit DC1 is configured to output a signal needed forreading a signal from a sensor, to the sensor when the signal line ML isselected.

In a period during which the signal line ML is not selected, the sensorcircuit DC1 can bring the signal line ML into, for example, a floatingstate or can output a constant voltage to the signal line ML. Note thatthe constant voltage corresponds to, for example, a common voltage thatis supplied to the display element in some cases.

The value of the self capacitance of the conductive film C (g, h), theconductive film C1, or the conductive film C2 is larger when an objectsuch as a finger or a pen approaches the conductive film C (g, h), theconductive film C1, or the conductive film C2 than when the object doesnot approach.

For example, a current measurement unit 311 and a pulse signal outputcircuit 312 can be used in the sensor circuit DC1 (see FIG. 9A). Thecurrent measurement unit 311 and the pulse signal output circuit 312 areconnected in series between the driver circuit 703 and a ground line313, for example. Note that the potential supplied to the ground line313 is not necessarily 0 V.

The pulse signal output circuit 312 outputs a pulse signal to theconductive film C (g, h), the conductive film C1, the conductive filmC2, or the like through the driver circuit 703. For example, the currentmeasurement unit 311 senses the amount of current. Thus, a touch can besensed.

For example, a resistor 314 and a voltage measurement unit 315 can beused in the current measurement unit 311 (see FIG. 9B). Voltage betweenboth terminals of the resistor 314 is measured by the voltagemeasurement unit 315, so that the value of current flowing through thecurrent measurement unit 311 can be measured. Note that the currentvalue is measured here, but one embodiment of the present invention isnot limited to this.

For example, a circuit having a function of measuring an integral valueof current can be used in the sensor circuit DC1. Specifically, anintegrator circuit can be formed with an operational amplifier 317. Forexample, a capacitor 316 and the operational amplifier 317 can be usedin the sensor circuit DC1 (see FIG. 9C).

For example, an amplifier circuit capable of amplifying a change inpotential can be used in the sensor circuit DC1. Thus, the amplifiercircuit can amplify the change in potential in accordance with theamount of the current flowing through the signal line ML (g, h).Consequently, current can be converted into potential, and a change inthe converted potential can be amplified and supplied to an externalcircuit as a sensing signal.

Data sensed by the sensor circuit DC1 is sent to a next circuit.Examples of the next circuit include a memory circuit and a signalprocessing circuit. The next circuit can determine which position istouched. Note that the next circuit may be placed in the sensor circuitDC1.

Next, timing when a signal is supplied to the plurality of conductivefilms C or the plurality of signal lines ML is described (see FIG. 10).For example, signals are sequentially supplied to the plurality ofsignal lines ML from the pulse signal output circuit 312 in the sensorcircuit DC1 through the driver circuit 703.

For example, a signal line ML is selected from the top to the bottom. Inother words, the signal lines ML are sequentially selected from thesignal line ML (1, 1) in the first row to the signal line ML (p, q) inthe last row, and the conductive films C are sequentially selected oneby one. Current flows between the sensor circuit DC1 and the selectedsignal line ML (g, h) and between the sensor circuit DC1 and theselected conductive film C (g, h).

The sensor circuit DC1 outputs a pulse signal to the signal line ML (g,h) and the conductive film C (g, h) and senses current flowing at thetime, whereby sensing can be performed.

In Embodiment 1, one embodiment of the present invention has beendescribed. Other embodiments of the present invention are described inEmbodiments 2 to 12. Note that one embodiment of the present inventionis not limited thereto. In other words, various embodiments of theinvention are described in this embodiment and the other embodiments,and one embodiment of the present invention is not limited to aparticular embodiment. Although the example in which one embodiment ofthe present invention is applied to the touch sensor has been described,one embodiment of the present invention is not limited thereto.Depending on circumstances or conditions, one embodiment of the presentinvention may be applied to various sensors, for example. Alternatively,depending on circumstances or conditions, one embodiment of the presentinvention is not necessarily applied to a touch sensor.

This embodiment shows an example of a basic principle. Thus, part or thewhole of this embodiment can be freely combined with, applied to, orreplaced with part or the whole of any of the other embodiments.

Embodiment 2

The structures of the input device are described in Embodiment 1. Theinput device can be combined with various devices. For example, it ispossible to form an in-cell display device in which the input device anda display element or a TFT are integrated in an element substrate (TFTsubstrate). In that case, the device has an output function ofdisplaying an image and an input function of reading a signal from asensor.

In this embodiment, a structure of an input/output device of oneembodiment of the present invention is described with reference to FIGS.11A to 11D. Note that description of the same portions as those inEmbodiment 1 is omitted in some cases.

FIGS. 11A to 11D illustrate the structure of an input/output device 700of one embodiment of the present invention.

FIG. 11A is an example of a block diagram illustrating the structure ofthe input/output device 700 one embodiment of the present invention.

FIG. 11B is an example of a block diagram for explaining details of partof the input/output device 700 illustrated in FIG. 11A.

FIG. 11C is an example of a cross section schematic diagram of theinput/output device 700 taken along the cutting plane line W1-W2 in FIG.11B. Note that, the signal line ML1 and the signal line ML2 seem to havedifferent heights in FIG. 11C, but one embodiment of the presentinvention is not limited to this. In the cross-sectional view, thesignal line ML1 and the signal line ML2 may be provided at the sameheight.

FIG. 11D is an example of a circuit diagram illustrating a displayelement 750 (i, j) and a pixel circuit which can be used in a pixel 702(i, j).

Note that the input/output device 700 differs from the input device 700Tin FIGS. 1A to 1C in that the input/output device 700 includes a displaydevice. In other words, the input/output device 700 has portions similarto those of the input device 700T. Thus, the above description of theinput device 700T can apply to the input/output device 700. Here, theabove description is referred to for the similar structures, anddifferent structures are described in detail.

Note that the input/output device 700 may have a structure in which theinput device 700T is added to a display device. Alternatively, theinput/output device 700 may have a structure in which a member is usedin common as a part of the display device and a part of the input device700T. In that case, the member has a function of the part of the displaydevice and a function of the part of the input device 700T. FIGS. 11A to11D illustrate an example of the case where a member has a function of apart of the display device and a function of a part of the input device700T.

<Structure Example 1 of Input/Output Device>

The input/output device 700 described in this embodiment includes thedisplay device and the input device 700T (see FIG. 11A). In other words,the input/output device 700 has a structure in which the input device700T is added in the display device and is partly incorporated in partof the display device. Thus, a member has a function of part of thedisplay device and a function of part of the input device 700T.

The input/output device 700 has a function of sensing an objectapproaching a display surface side of the display device (see FIG. 11C).

The display device (output device) includes the pixel 702 (i, j) in aregion where the conductive film C1 is provided and a pixel 702 (i, k)in a region where the conductive film C2 is provided (see FIGS. 11B and11 C). Here, each of i, j, and k is a variable and an integer greaterthan or equal to 1. In addition, the value of k is different from thatof j.

For example, the pixels 702 may be arranged in a matrix. For example,the pixel 702 (i, j) can be disposed in the same row as the pixel 702(i, k) and in a different column from the pixel 702 (i, k).

Note that a plurality of pixels is disposed in the region where theconductive film C1, the conductive film C2, or the like is provided. Forexample, the plurality of pixels 702 is provided in one conductive filmC1. The pixel 702 (i, j) is one of the plurality of pixels 702.Similarly, the plurality of pixels 702 is provided in one conductivefilm C2. The pixel 702 (i, k) is one of the plurality of pixels 702.

For example, the pixel 702 (i, j) includes the display element 750 (i,j), and the pixel 702 (i, k) includes a display element 750 (i, k). FIG.11D illustrates an example of a circuit of the pixel 702 (i, j). Notethat the pixel 702 (i, j) may include a plurality of display elements.

The input/output device includes a display device, a plurality ofconductive films configured to be capacitively coupled to an objectapproaching a display surface side of the display device, a drivercircuit that selects one from the plurality of conductive films in apredetermined order, and a sensor circuit configured to supply a searchsignal and a sensing signal. Thus, the object approaching the displaysurface side of the display device can be sensed on the basis of apotential that is changed in accordance with the search signal and thecapacitance coupled to the conductive film. Consequently, a novelinput/output device that is highly convenient or reliable can beprovided.

The input/output device 700 includes a plurality of pixels (see FIG.11B). For example, the input/output device 700 includes n pixels in thehorizontal direction and m pixels in the vertical direction. That is,the input/output device 700 includes the pixels 702 (i, j) arranged in amatrix of m rows by n columns. Note that m is an integer greater than orequal to i, and n is an integer greater than or equal to j.

The pixel 702 (i, j) can have a pixel circuit that drives the displayelement 750 (i, j), and the pixel 702 (i, k) can have a pixel circuitthat drives the display element 750 (i, k). For example, the pixelcircuit illustrated in FIG. 11D can be used for the pixel 702 (i, j).Note that the pixel 702 (i, j) or the pixel 702 (i, k) may include aplurality of display elements.

In addition, the input/output device 700 can include a scan line G (i)electrically connected to pixels 702 (i, 1) to 702 (i, n) arranged inthe same row. Note that, in addition to the scan line G (i), anotherwiring may be connected to the pixel 702 (i, j) or the pixels 702 (i, 1)to 702 (1, n).

The scan line G (i) has a function of selecting a pixel connected to thescan line G (i), for example. Alternatively, the scan line G (i) has afunction of supplying a selection signal to a pixel, for example. Thescan line G (i) may supply not only the selection signal but alsoanother signal. Note that the scan line G (i) is called gate line, gatesignal line, scan line, wiring, first wiring, or the like in some cases.

In addition, the input/output device 700 can include a signal line S (j)electrically connected to pixels 702 (1, j) to 702 (m, j) arranged inthe same column. Similarly, the input/output device 700 can include asignal line S (k) electrically connected to pixels 702(1, k) to 702 (m,k) arranged in the same column. Note that not only the signal line S (j)but also another wiring may be connected to the pixel 702 (i, j).

The signal line S (j) has a function of supplying a video signal to apixel connected to the signal line S (j), for example. Alternatively,the signal line S (j) has a function of supplying or writing a videosignal to a pixel, for example. The signal line S (i) may supply notonly the video signal but also another signal. Note that the signal lineS (i) is called source line, source signal line, data line, wiring,first wiring, or the like in some cases.

The input/output device 700 includes, for example, a driver circuit GDelectrically connected to scan lines G (1) to G (m). For example, thedriver circuit GD has functions of selecting one of the scan lines G (1)to G (m) and supplying a selection signal to the scan lines G (1) to G(m), the pixel 702 (i, j), or the like. Note that the driver circuit GDmay supply not only the selection signal but also another signal.

The driver circuit GD is called gate line driver circuit, gate signalline driver circuit, scan line driver circuit, scan circuit, circuit,first circuit, or the like in some cases.

The input/output device 700 includes a driver circuit SD electricallyconnected to signal lines S (1) to S (n), for example. The drivercircuit SD has a function of supplying an image signal to the signallines S (1) to S (n), the pixel 702 (i, j), or the like. Note that thedriver circuit SD may supply not only the video signal but also anothersignal.

The driver circuit SD is called source line driver circuit, sourcesignal line driver circuit, video signal line driver circuit, data linecircuit, circuit, first circuit, or the like in some cases.

<<Structure Example>>

The input/output device 700 of one embodiment of the present inventionincludes the display device or the input device 700T.

The input/output device 700 of one embodiment of the present inventionincludes the pixel 702 (i, j) and the pixel 702 (i, k).

The input/output device 700 of one embodiment of the present inventionincludes the display element 750 (i, j) and the display element 750 (i,k).

The input/output device 700 of one embodiment of the present inventionincludes the scan line G (i), the signal line S (j), the signal lineS(k), the driver circuit GD, and the driver circuit SD.

<<Input Device>>

For the input/output device 700 of one embodiment of the presentinvention, an input device including the conductive film C1 or theconductive film C2 which is configured to be capacitively coupled to anobject approaching a display surface side of the display device can beused.

For example, a light-transmitting conductive film can be used as theconductive film C1 or the conductive film C2. Alternatively, aconductive film having an opening, a slit, a comb shape, a latticeshape, or the like in a region where the display element is provided canbe used as conductive film C1 or the conductive film C2. Thus, theconductive film C1 or the conductive film C2 can be provided between thedisplay element and a user.

<<Display Device>>

For example, an active matrix display device or a passive matrix displaydevice can be used. Instead of using the display device, a lightingdevice with which a video or an image is not displayed may be used.

<<Display Element 750 (i, j), Display Element 750 (i, k)>>

For example, a display element that has a function of controlling lightreflection or light transmission or a light-emitting element can be usedas the display element 750 (i, j) or the display element 750 (i, k).

Specifically, a combined structure of a polarizing plate and a liquidcrystal element, a MEMS shutter display element, or the like can be usedas the display element 750 (i, j) or the display element 750 (i, k).

Specifically, for example, an organic electroluminescent element, anLED, or an inorganic electroluminescent element can be used as thedisplay element 750 (i, j) or the display element 750 (i, k).

<<Pixels 702 (i, j), 702 (i, k)>>

For example, a switching element SW, a capacitor Cp, and the like can beused in the pixel 702 (i, j) or the pixel 702 (i, k). FIG. 11D shows anexample of the pixel 702 (i, j).

Specifically, a transistor can be used as a switching element SW. Forexample, the transistor that can be used in the driver circuit 703described in Embodiment 1 can be used as the switching element SW.

For example, the driver circuit 703 and the pixel 702 (i, j) may beformed over different substrates. In that case, each wiring of the pixel702 (i, j) is connected to the driver circuit 703 through a connectionterminal, a wiring, an anisotropic conductive particle, a silver paste,a flexible printed circuit (FPC), or a bump, for example.

For example, a transistor that can be used in the driver circuit 703 anda transistor that can be used in the pixel 702 (i, j) may be formed overthe same substrate. In that case, the driver circuit 703 and the pixel702 (i, j) can be formed through the same manufacturing process.

For example, in the case where the driver circuit 703 and the pixel 702(i, j) are formed over the same substrate, a special connection portionis not needed, so that contact failure generated in the connectionportion can be prevented. As a result, the reliability can be improved.In addition, the driver circuit 703 and the pixel 702 (i, j) can beformed through the same manufacturing process. Furthermore, themanufacturing cost can be reduced. Note that one embodiment of thepresent invention is not limited to the above structures.

<<Scan Line G (i), Signal Line S (j)>>

A conductive material can be used for the scan line G (i) or the signalline S (I).

For example, a material that can be used for the conductive film C1, theconductive film C2, the signal line ML1, the signal line ML2, thecontrol line CL, or the like can be used for the scan line G (i) or thesignal line S (j).

<<Driver Circuit GD>>

A variety of sequential circuits, such as a shift register, can be usedas the driver circuit GD.

For example, a transistor including a semiconductor film that can beformed by the same step as a semiconductor film of a transistor that isused in the driver circuit 703, the pixel 702 (i, j), the pixel 702 (i,k), or the like described in Embodiment 1 can be used in the drivercircuit GD.

<<Driver Circuit SD>>

A variety of sequential circuits, such as a shift register, can be usedas the driver circuit SD.

For example, an integrated circuit can be used as the driver circuit SD.Specifically, an integrated circuit formed over a silicon substrate canbe used. Note that the whole of the driver circuit SD is not necessarilyformed over the silicon substrate and part of the driver circuit SD maybe formed over the silicon substrate.

For example, a chip on glass (COG) method can be used to mount thedriver circuit SD. Specifically, an anisotropic conductive film can beused to mount the integrated circuit on a pad.

For example, a transistor that can be formed through the same process asa transistor that can be used in the driver circuit 703, the pixel 702(i, j), the pixel 702 (i, k), the driver circuit GD, or the likedescribed in Embodiment 1 can be used in part or the whole of the drivercircuit SD.

<Structure Example 2 of Input/Output Device>

Another structure of the input/output device of one embodiment of thepresent invention is with reference to FIGS. 11A to 11D, FIG. 12, FIG.13, and FIGS. 14A to 14C.

Note that the above description is referred to for similar structures,the structure of using a wiring COM and the structure of using liquidcrystal elements in the pixels 702 (i, j) and (i, k) are described indetail.

FIG. 12 and FIG. 13 each illustrate an example of a structure of thedriver circuit 703 that can be used for the input/output device 700 ofone embodiment of the present invention. FIG. 12 illustrates an exampleof a structure of the driver circuit 703. FIG. 13 illustrates an exampleof a structure of the driver circuit 703B. The driver circuit 703B isconnected to the sensor circuit DC11 and the sensor circuit DC12.

FIGS. 14A to 14C illustrate a structure of a pixel that can be used inthe input/output device 700 of one embodiment of the present invention.FIG. 14A illustrates examples of top views of the pixel 702 (i, j) andthe pixel 702 (i, k). FIG. 14B illustrates an example of across-sectional view of the pixel 702 (i, j) taken along the cuttingplane line W3-W4 in FIG. 14A and an example of a cross-sectional view ofthe pixel 702 (i, k) taken along the cutting plane line W5-W6 in FIG.14A.

The input/output device 700 described in this embodiment can includesthe wiring COM, for example (see FIG. 11A).

The wiring COM is electrically connected to the driver circuit 703 andhas a function of supplying a predetermined potential. For example, acommon potential that is supplied to a plurality of display elements canbe supplied to the wiring COM.

For example, the driver circuit 703 has a function of letting currentflow between the signal line ML2 and the wiring COM or between a signalline ML other than the signal line ML1 and the wiring COM in a periodduring which the signal line ML1 is selected. Alternatively, the drivercircuit 703 has a function of preventing current from flowing betweenthe signal line ML1 and the wiring COM in the period during which thesignal line ML1 is selected. In other words, the driver circuit 703 hasa function of letting current flow between the signal line ML2 and thewiring COM in the period during which the signal line ML2 is notselected.

The above can apply to the case in which the signal line ML2 isselected. That is, the driver circuit 703 has a function of preventingcurrent from flowing between the signal line ML2 and the wiring COM inthe period during which the signal line ML2 is selected.

Furthermore, the driver circuit 703 has a function of letting currentflow between the signal line ML1 and the wiring COM or between a signalline ML other than the signal line ML2 and the wiring COM in a periodduring which the signal line ML2 is selected. Alternatively, the drivercircuit 703 has a function of preventing current from flowing betweenthe signal line ML2 and the wiring COM in the period during which thesignal line ML2 is selected. In other words, the driver circuit 703 hasa function of letting current flow between the signal line ML1 and thewiring COM in the period during which the signal line ML1 is notselected.

These operations area controlled by a shift register included in thedriver circuit 703, for example. The shift register sequentially scansand outputs selection signals. As a result, conduction states ofswitches connected to the signal line ML1, the signal line ML2, and thelike are changed. Consequently, the conduction state between the wiringCOM and the signal line ML1, the signal line ML2, and the like orbetween the sensor circuit DC1 and the signal line ML1, the signal lineML2, and the like are switched.

The display element 750 (i, j) includes a layer 753 containing a liquidcrystal material, the conductive film C1, and a pixel electrode 751 (i,j) (see FIGS. 14A and 14B). The pixel electrode 751 (i, j) is providedsuch that an electric field that controls the orientation of the liquidcrystal material is formed between the conductive film C1 and the pixelelectrode 751 (i, j). For example, the conductive film C1 can have afunction of a display element. In other words, the conductive film C1has a function of an electrode of a touch sensor and a function as anelectrode of a display element. Note that arrows BL in the drawings showthe direction in which light emitted by a backlight travels.

The display element 750 (i, k) includes the layer 753 containing aliquid crystal material, the conductive film C2, and a pixel electrode751 (i, k). The pixel electrode 751 (i, k) is provided such that anelectric field that controls the orientation of the liquid crystalmaterial is formed between the conductive film C2 and the pixelelectrode 751 (i, k).

For example, the conductive film C1, the conductive film C2, theconductive film C (g, h), or the like has a function as part of adisplay element. For example, the conductive film C1, the conductivefilm C2, the conductive film C (g, h), or the like has a function of acommon electrode of a plurality of display elements. In other words, theconductive film C1, the conductive film C2, the conductive film C (g,h), or the like has a function of an electrode of a touch sensor and afunction of an electrode of a display element.

For example, the pixel electrode 751 (i, j), the pixel electrode 751 (i,k), or the like can be disposed over the conductive film C1 or theconductive film C2 with an insulating film positioned therebetween (seeFIGS. 14A and 14B).

The pixel electrode 751 (i, j) and the pixel electrode 751 (i, k) canhave, for example, a comb shape, an opening, or a slit. Thus, an FFSmode liquid crystal element in which a common electrode is disposedbelow the pixel electrode can be used as the display element (see FIGS.14A and 14B). Note that one embodiment of the present invention is notlimited thereto.

For example, the pixel electrode 751 (i, j), the pixel electrode 751 (i,k), or the like can be disposed below the conductive film C1 or theconductive film C2 with an insulating film positioned therebetween.

The conductive film C1 or the conductive film C2 can have, for example,a comb shape, an opening, or a slit. Thus, an FFS mode liquid crystalelement in which a common electrode is disposed over the pixel electrodecan be used as the display element (see FIG. 14C).

The pixel electrode and the common electrode both can have, for example,a comb shape, an opening, or a slit. Thus, an IPS mode liquid crystalelement can be used as the display element (see FIGS. 15A and 15B).

For example, the pixel electrode 751 (i, j), the pixel electrode 751 (i,k), or the like can be disposed under the conductive film C1 or theconductive film C2 with an insulating film positioned therebetween (seeFIG. 15B). Note that one embodiment of the present invention is notlimited thereto.

For example, the pixel electrode 751 (i, j), the pixel electrode 751 (i,k), or the like can be disposed over the conductive film C1 or theconductive film C2 with an insulating film positioned therebetween.

For example, the conductive film C1 or the conductive film C2 and thepixel electrode 751 (i, j) or the pixel electrode 751 (i, k) can beformed on the same plane (see FIG. 15C).

Note that one embodiment of the present invention is not limited to thecase in which the conductive film C1 or the conductive film C2 has afunction of an electrode of a touch sensor and a function of anelectrode of a display element.

For example, a display element that includes a conductive film differentfrom the conductive film C1 or the conductive film C2 having a functionof an electrode of a touch sensor can be used. Specifically, a displayelement that includes the pixel electrode 751 (i, j) and a commonelectrode 754 can be used.

For example, FIG. 16A corresponds to FIG. 14C. Similarly, FIG. 16Ccorresponds to FIG. 14B. For example, FIG. 16E corresponds to FIG. 15B.Similarly, FIG. 16F corresponds to FIG. 15C.

For example, the conductive film C1 that has a function of an electrodeof a touch sensor can be disposed over an insulating film (see FIGS. 16Aand 16B).

For example, the conductive film C1 that has a function of an electrodeof a touch sensor can be disposed below the pixel electrode 751 (i, j)or the common electrode 754 with the insulating film positionedtherebetween (see FIGS. 16C and 16D). Note that one embodiment of thepresent invention is not limited thereto.

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device including a liquid crystal element,a plurality of conductive films configured to control the orientation ofthe liquid crystal material and be capacitively coupled to an objectapproaching a display surface side of the display device, a sensorcircuit configured to supply a search signal and a sensing signal, and adriver circuit configured to select one from the plurality of conductivefilms in a predetermined order and be electrically connected to thesensor circuit or a wiring.

Thus, pixels can be rewritten in a predetermined order, and the objectapproaching the display surface side of the display device including aliquid crystal element can be sensed on the basis of a potential that ischanged in accordance with the search signal and the capacitance coupledto the conductive film. Consequently, a novel input/output device thatis highly convenient or reliable can be provided.

The input/output device 700 includes a base 710 and a base 770 includinga region overlapping with the base 710 (see FIG. 14B).

The input/output device 700 includes a sealant (not shown) with whichthe base 770 and the base 710 are bonded to each other.

Note that the input/output device 700 includes the layer 753 containinga liquid crystal material in a region surrounded by the base 710, thebase 770, and the sealant.

Individual components included in the input/output device 700 aredescribed below. Note that these components cannot be clearlydistinguished and one component may also serve as another component orinclude part of another component.

For example, the conductive film C1 is configured to be capacitivelycoupled to an approaching object and has a function of a commonelectrode of the display element 750 (i, j). The conductive film C2 isconfigured to be capacitively coupled to an approaching object and has afunction of a common electrode of the display element 750 (i, k). Thesignal line ML1 is a wiring having a function of supplying a signal fora touch sensor and a function of a common wiring connected to an commonelectrode of a display element. Similarly, the signal line ML2 is awiring having a function of supplying a signal for a touch sensor and afunction of a common wiring connected to an common electrode of adisplay element.

<<Structure Example>>

The input/output device of one embodiment of the present inventionincludes the wiring COM in addition to the above-described structure.

The input/output device of one embodiment of the present inventionincludes the layer 753 containing a liquid crystal material and thepixel electrode 751 (i, j) or the pixel electrode 751 (i, k).

<<Wiring COM>>

A conductive material can be used for the wiring COM or the like.

For example, a material that can be used for the conductive film C1, theconductive film C2, the conductive film C (g, h), the signal line ML1,the signal line ML2, the signal line ML (g, h), the control line CL, orthe like can be used for the wiring COM or the like.

For example, a wiring having a function of supplying a ground potential,a common potential, a power supply potential, or the like can be used asthe wiring COM.

For example, a potential to be supplied to the signal line ML1 or thesignal line ML2 can be used as a predetermined potential supplied by thewiring COM. Alternatively, a wiring that supplies different potentialscan be used as the wiring COM.

For example, a potential supplied to a terminal of the display element750 (i, j), the display element 750 (i, k), or the like can be used as apredetermined potential supplied by the wiring COM.

Specifically, a wiring having a function of supplying different twopotentials alternately can be used as the wiring COM. Thus, voltageswith inverse polarities can be supplied to the display element 750 (i,j), the display element 750 (i, k), or the like. That is, for commoninversion driving of the display element, the potential of the wiringCOM may be changed in a pulsed manner. As a result, for example, aliquid crystal element is used as the display element 750 (i, j), thedisplay element 750 (i, k), or the like to improve the reliability ofthe input/output device 700. Furthermore, the power consumption can bereduced.

<<Driver Circuit 703>>

For example, the driver circuit 703 can include a shift register 301 orthe like (see FIG. 12). Thus, one or more signal lines can be selectedfrom the plurality of signal lines ML in a predetermined order and aselection signal can be supplied. The selection signal is supplied to,for example, a selection circuit 302.

For example, the driver circuit 703 can include the selection circuit302. The selection circuit 302 includes a plurality of switches, forexample. Moreover, the driver circuit 703 may include an invertercircuit in order to invert the selection signal. Thus, the sensorcircuit DC1 or the wiring COM can be selected in accordance with theselection signal, and current can flow between the selected sensorcircuit DC1 and the signal line ML or between the selected wiring COMand the signal line ML.

With the use of the shift register 301, a selection circuit can besequentially selected from a plurality of selection circuits. Forexample, one can be selected from the signal line ML1, the signal lineML2, and the signal line ML3. As a result, current can flow between thesensor circuit DC1 and one signal line electrically connected to oneselection circuit to which a selection signal is supplied.Alternatively, current can flow between the wiring COM and a signal lineelectrically connected to a selection circuit to which a selectionsignal line is not supplied. That is, by the selection signal outputfrom the shift register, the conduction (on/off) state of the switchconnected to the signal line ML (g, h) can be controlled. As a result,the conduction state between the signal line ML (g, h) and the wiringCOM and the conduction state between the signal line ML (g, h) and thesensor circuit DC1 can be controlled.

<<Display Element 750 (i, j), Display Element 750 (i, k)>>

For example, a liquid crystal element that has a function of controllinglight reflection or light transmission can be used as the displayelement 750 (i, j) or the display element 750 (i, k).

Specifically, a liquid crystal element that can be driven by any of thefollowing driving methods can be used: an in-plane switching (IPS) mode,a twisted nematic (TN) mode, a fringe field switching (FFS) mode, anaxially symmetric aligned micro-cell (ASM) mode, an opticallycompensated birefringence (OCB) mode, a ferroelectric liquid crystal(FLC) mode, an antiferroelectric liquid crystal (AFLC) mode, and thelike.

Alternatively, a liquid crystal element that can be driven by a drivingmethod such as a vertical alignment (VA) mode, specifically, amulti-domain vertical alignment (MVA) mode, a patterned verticalalignment (PVA) mode, or an advanced super view (ASV) mode can be used.

<<Layer 753 Containing Liquid Crystal Material>>

For example, thermotropic liquid crystal, low-molecular liquid crystal,high-molecular liquid crystal, polymer dispersed liquid crystal,ferroelectric liquid crystal, or anti-ferroelectric liquid crystal canbe used. These liquid crystal materials exhibit a cholesteric phase, asmectic phase, a cubic phase, a chiral nematic phase, an isotropicphase, or the like depending on conditions. Alternatively, a liquidcrystal material that exhibits a blue phase can be used for the liquidcrystal layer 753.

<<Pixel Electrode 751 (i, j) or Pixel Electrode 751 (i, k)>>

A conductive material can be used for the pixel electrode 751 (i, j),the pixel electrode 751 (i, k), or the like.

For example, a material that can be used for the conductive film C1, theconductive film C2, the signal line ML1, the signal line ML2, or thelike can be used for the pixel electrode 751 (i, j) or the pixelelectrode 751 (i, k).

<<Base 710, Base 770>>

A material having heat resistance high enough to withstand heattreatment in the manufacturing process can be used for the base 710 or770. Note that a light-transmitting material can be used for the base710 and the base 770.

For example, a large-sized glass substrate having any of the followingsizes can be used as the base 710 or 770: the 6th generation (1500mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8th generation(2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm), and the 10thgeneration (2950 mm×3400 mm). Thus, a large-sized display device can bemanufactured.

For the base 710 or 770, an organic material, an inorganic material, acomposite material of an organic material and an inorganic material, orthe like can be used. For example, an inorganic material such as glass,ceramic, or metal can be used for the base 710 or 770.

Specifically, non-alkali glass, soda-lime glass, potash glass, crystalglass, quartz, sapphire, or the like can be used for the base 710 or770. Specifically, an inorganic oxide film, an inorganic nitride film, amaterial containing an inorganic oxynitride, or the like can be used forthe base 710 or 770. For example, a material containing silicon oxide,silicon nitride, silicon oxynitride, or aluminum oxide can be used forthe base 710 or 770. For example, stainless steel or aluminum can beused for the base 710 or 770.

For example, a single-crystal semiconductor substrate or apolycrystalline semiconductor substrate made of silicon or siliconcarbide, a compound semiconductor substrate made of silicon germanium orthe like, or an SOI substrate can be used as the base 710 or 770. Thus,a semiconductor element can be provided over the base 710 or 770.

For example, an organic material such as a resin, a resin film, orplastic can be used for the base 710 or 770. Specifically, a resin filmor resin plate of polyester, polyolefin, polyamide, polyimide,polycarbonate, an acrylic resin, or the like can be used for the base710 or 770.

For example, a composite material formed by attaching a metal plate, athin glass plate, or a film of an inorganic material to a resin film orthe like can be used for the base 710 or 770. For example, a compositematerial formed by dispersing a fibrous or particulate metal, glass, aninorganic material, or the like into a resin film can be used as thebase 710 or 770. For example, a composite material formed by dispersinga fibrous or particulate resin, an organic material, or the like into aninorganic material can be used as the base 710 or 770.

Furthermore, a single-layer material or a layered material in which aplurality of layers are stacked can be used for the base 710 or 770. Forexample, a layered material in which a base, an insulating film thatprevents diffusion of impurities contained in the base, and the like arestacked can be used for the base 710 or 770. Specifically, a materialobtained by stacking glass and one or a plurality of films that areselected from a silicon oxide layer, a silicon nitride layer, a siliconoxynitride layer, and the like and that prevent diffusion of impuritiescontained in the glass can be used for the base 710 or 770.Alternatively, a layered material in which a resin and a film forpreventing diffusion of impurities that penetrate the resin, such as asilicon oxide film, a silicon nitride film, and a silicon oxynitridefilm are stacked can be used for the base 710 or 770.

Specifically, a resin film, a resin plate, a stack, or the like ofpolyester, polyolefin, polyamide, polyimide, polycarbonate, an acrylicresin, or the like can be used for the base 710 or 770.

Specifically, a material including polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, an acrylic resin, aurethane resin, an epoxy resin, a resin having a siloxane bond such assilicone, or the like can be used for the base 710 or 770.

Specifically, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), acrylic, or the like can be used for thebase 710 or 770.

Alternatively, paper, wood, or the like can be used for the base 710 or770.

For example, a flexible substrate can be used as the base 710 or 770.

Note that a transistor, a capacitor, or the like can be directly formedon the substrate. Alternatively, a method in which a transistor, acapacitor, or the like is formed over a substrate for use inmanufacturing processes which can withstand heat applied in themanufacturing process and is transferred to the base 710 or 770 can beemployed. Thus, a transistor, a capacitor, or the like can be formedover a flexible substrate, for example.

<Structural Example 3 of Input/Output Device>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIG. 13.

Note that the input/output device described here differs from theaforementioned input/output device 700 in that the input/output deviceincludes a plurality of sensor circuits and the driver circuit 703Binstead of the driver circuit 703. Here, the above description isreferred to for the similar structures, and different structures aredescribed in detail.

The wiring COM is electrically connected to the driver circuit 703B, andhas a function of supplying a predetermined potential.

The driver circuit 703B can select two or more selection circuits fromthe plurality of selection circuits. Therefore, the driver circuit 703Bhas a function of selecting at least two of the signal line ML1, thesignal line ML2, the signal line ML3, the signal line ML4, the signalline MLS, and the signal line ML6, for example.

The driver circuit 703B has a function of, for example, letting currentflow between the signal line ML1 and the sensor circuit DC11 and lettingcurrent flow between the signal line ML2 and the sensor circuit DC12 ina period during which the signal line ML1 and the signal line ML2 areselected. The driver circuit 703B has a function of, for example,letting current flow between the signal lines ML1 and ML2 and the wiringCOM in a period during which the signal line ML1 and the signal line ML2are not selected. Here, the case where the signal line ML1 and thesignal line ML2 are selected is described, the same can be applied tothe case where other signal lines are selected. In addition, the casewhere two selection circuits are selected from the plurality ofselection circuits are described here, but the number of selectedcircuits may be three or more.

Note that the plurality of signal lines ML selected at the same time maybe positioned apart from each other. For example, the signal lines MLselected at the same time are not limited to a combination of the signalline ML1 and the signal line ML2 and may be a combination of the signalline ML1 and the signal line ML6. In the case where signal lines MLpositioned apart from each other are selected, crosstalk can beprevented.

The sensor circuit DC11 and the sensor circuit DC12 have a functionsimilar to that of the sensor circuit DC1, and for example, have afunction of supplying a search signal.

The input/output device of one embodiment of the present inventionincludes a display device including a liquid crystal element, aplurality of conductive films that has a function of controlling theorientation of a liquid crystal material and that is configured to becapacitively coupled to an object approaching a display surface side ofthe display device, a plurality of sensor circuits having a function ofsupplying a search signal and a sensing signal, and a driver circuitwhich has a function of selecting two or more conductive films from aplurality of conductive films in a predetermined order and which iselectrically connected to the sensor circuit or a wiring.

Thus, pixels can be rewritten in a predetermined order, and the objectapproaching the display surface side of the display device including aliquid crystal element can be sensed on the basis of a potential that ischanged in accordance with the search signal and the capacitance coupledto the conductive film. Consequently, a novel input/output device thatis highly convenient or reliable can be provided.

<<Driver Circuit 703B>>

For example, a shift register having a function of supplying a selectionsignal can be used for the driver circuit 703B (see FIG. 13).

For example, a selection circuit that controls a conduction statebetween the sensor circuit DC11 or the wiring COM and the signal line inaccordance with the selection signal can be used for the driver circuit703B. Alternatively, a selection circuit that controls a conductionstate between the sensor circuit DC12 or the wiring COM and the signalline in accordance with the selection signal can be used for the drivercircuit 703B.

Thus, two or more selection circuits can be selected from a plurality ofselection circuits in a predetermined order with use of the shiftregister. As a result, current can flow between the sensor circuit DC11and a signal line electrically connected to a selection circuit to whichthe selection signal is supplied, between sensor circuit DC12 and asignal line electrically connected to another selection circuit to whichthe selection signal is supplied, and between the wiring COM and asignal line electrically connected to a selection circuit to which theselection signal is not supplied.

<<Sensor Circuit DC11, Sensor Circuit DC12>>

For example, the structure that can be used for the sensor circuit DC1described in Embodiment 1 can be used for the sensor circuit DC11 andthe sensor circuit DC12 in this embodiment.

This embodiment is obtained by performing change, addition,modification, removal, application, superordinate conceptualization, orsubordinate conceptualization on part or the whole of anotherembodiment. Thus, part or the whole of this embodiment can be freelycombined with, applied to, or replaced with part or the whole of anotherembodiment.

Embodiment 3

In this embodiment, a structure of an input device 700TC which is oneembodiment of the present invention is described with reference to FIGS.17A to 17C.

Note that the input device 700TC differs from the input device 700Tdescribed with reference to FIGS. 1A to 1C in that the conductive filmC1 and the conductive film C2 are arranged such that an electric fieldthat is shielded by an approaching object is formed between theconductive film C1 and the conductive film C2, that the driver circuit703C is included instead of the driver circuit 703, that a sensorcircuit DC2 is included instead of the sensor circuit DC1, and signalssupplied to and read from the conductive film C1 and the conductive filmC2.

Note that the layouts and the structures of the conductive film C1, theconductive film C2, and the like are similar to those of the inputdevice 700T described with reference to FIGS. 1A to 1C. Thus, thedescription for the input device 700T can be similarly applied to theinput device 700TC of one embodiment of the present invention. Here, theabove description is referred to for the similar structures, anddifferent structures will be described in detail.

<Structure Example of Input Device>

The input device 700TC described in this embodiment includes theconductive film C1, the conductive film C2, the signal line ML1, and thesignal line ML2 (see FIG. 17B) like the input device 700T. Note thatconductive films selected from the plurality of conductive films C canbe used for the conductive film C1 and the conductive film C2 (see FIG.17A).

The conductive film C2 has a region not overlapping with the conductivefilm C1. For example, a conductive film adjacent to the conductive filmC1 can be used as the conductive film C2. Alternatively, a conductivefilm may be provided between the conductive film C1 and the conductivefilm C2.

The signal line ML1 is electrically connected to the conductive film C1.The signal line ML2 is electrically connected to the conductive film C2(see FIG. 17B).

The conductive film C1 and the conductive film C2 are configured to becapacitively coupled to each other (see FIG. 17C). For example, theplurality of conductive films C are capacitively coupled to one another.Specifically, capacitive coupling is formed between the conductive filmC1 and the conductive film C2.

The capacitance value between the conductive films is changed by anobject approaching a region between the conductive films. Thus, anobject such as a finger or a pen approaching the region between theconductive film C1 and the conductive film C2 can be sensed with achange in the capacitance value between the conductive film C1 and theconductive film C2. In other words, the approach of an object such as afinger or a pen is sensed with a change in mutual capacitance betweenthe conductive film C1 and the conductive film C2.

As an example, the input device 700TC includes the driver circuit 703Cand the sensor circuit DC2 (see FIG. 17A). In some cases, the inputdevice 700TC does not include the driver circuit 703C, the sensorcircuit DC2, or the like, and another device or module includes thedriver circuit 703C, the sensor circuit DC2, or the like.

As an example, the driver circuit 703C may be provided in a mannersimilar to that of the driver circuit 703. For example, the drivercircuit 703C may be provided on the same substrate as the plurality ofconductive films C or the plurality of signal lines ML. Similarly, forexample, the sensor circuit DC2 may be provided in a manner similar tothat of the sensor circuit DC1.

The driver circuit 703C is electrically connected to the signal line ML1and the signal line ML2, for example.

The sensor circuit DC2 is electrically connected to the driver circuit703C, for example.

The driver circuit 703C has a function of selecting at least two of theplurality of signal lines ML, for example.

The driver circuit 703C has a function of sequentially selecting atleast two of the plurality of signal lines ML, for example.

The driver circuit 703C has a function of selecting at least two of theplurality of signal lines ML in an appropriate order, for example.

For example, the driver circuit 703C has a function of a multiplexer ora demultiplexer. The driver circuit 703C has a function of selecting thesignal line ML1 and the signal line ML2.

Specifically, the driver circuit 703C has a function of selecting twosignal lines from signal lines ML (1, 1) to ML (p, q) in a predeterminedorder. Alternatively, the driver circuit 703C has a function ofselecting at least two of the plurality of conductive films C.Alternatively, the driver circuit 703C has a function of selecting theconductive film C1 and the conductive film C2, for example.

Note that two driver circuits 703C may be provided, for example. One mayhave a function of selecting one signal line ML from the plurality ofsignal lines ML, and the other may have a function of selecting anothersignal line ML from the plurality of signal lines ML.

For example, the driver circuit 703C has a function of letting currentflow between each of the signal lines ML1 and ML2 and the sensor circuitDC2 in a period during which the signal lines ML1 and ML2 are selected.

Alternatively, the driver circuit 703C has a function of preventingcurrent from flowing between each of the signal lines ML1 and ML2 andthe sensor circuit DC2 in a period during which the signal lines ML1 andML2 are not selected.

Alternatively, the driver circuit 703C has a function of bringing thesignal lines ML1 and ML2 into a floating state in the period duringwhich the signal lines ML1 and ML2 are not selected.

Alternatively, the driver circuit 703C has a function of supplying apredetermined voltage, for example, a constant voltage, to the signallines ML1 and ML2, in the period during which the signal lines ML1 andML2 are not selected. Note that the driver circuit 703C is simply calledcircuit, first circuit, second circuit, or the like, in some cases.

For example, in the case where the driver circuit 703C is not used, theplurality of signal lines ML is connected to the sensor circuit DC2. Inthat case, each signal line ML needs a circuit for supplying a signal ora circuit for reading a signal in the sensor circuit DC2; alternatively,one sensor circuit DC2 needs to be connected to each of the signal linesML.

In the case where the driver circuit 703C is provided, for example, atleast two of the plurality of signal lines ML are selected, and theselected signal lines ML are changed every certain period; thus, thecircuit for supplying a signal or a circuit for reading a signal isprovided in accordance with the selected two signal lines ML. That is,it is not necessary that such a circuit be provided by the number ofsignal lines ML. Alternatively, because one sensor circuit DC2 isprovided with respect to the selected two signal lines ML, it is notnecessary to provide a plurality of sensor circuits DC2. Accordingly,the number or the size of circuits in the sensor circuit DC2 can bereduced. Alternatively, the number of sensor circuits DC2 can bereduced.

The sensor circuit DC2 has a function of supplying a search signal, forexample. Here, the search signal refers to, for example, a signalsupplied for sensing to the signal line ML (g, h) or the conductive filmC (g, h).

For example, the sensor circuit DC2 has a function of supplying a squarewave search signal. Alternatively, the sensor circuit DC2 has a functionof supplying a pulse signal. Alternatively, the sensor circuit DC2 has afunction of supplying a signal to a sensor.

Alternatively, the sensor circuit DC2 has a function of sensing a changein the capacitance value. Alternatively, the sensor circuit DC2 has afunction of sensing a current value. Alternatively, the sensor circuitDC2 has a function of sensing the amount of charge. Alternatively, thesensor circuit DC2 has a function of integrating a signal.Alternatively, the sensor circuit DC2 has a function of convertingcurrent into voltage. Alternatively, the sensor circuit DC2 has afunction of sensing a voltage value. Alternatively, the sensor circuitDC2 has a function of converting an analog signal into a digital signal.

The sensor circuit DC2 has a function of reading a signal from thesensor. Therefore, the sensor circuit DC2 is simply called circuit,first circuit, second circuit, or the like, in some cases.

The signal line ML1 has a function of receiving a search signal.

The signal line ML2 has a function of outputting a signal (current) thatchanges on the basis of the search signal and the capacitance value ofthe mutual capacitance formed between the conductive film C1 and theconductive film C2 (see FIG. 17C).

For example, when a pulse signal is supplied to the signal line ML1,current flows from the signal line ML1 to the signal line ML2 throughthe mutual capacitance formed between the conductive film C1 and theconductive film C2.

For example, when a finger or the like of a user of the input deviceapproaches the conductive film C1 or the conductive film C2, an electricfield formed between the conductive film C1 and the conductive film C2is partly blocked, so that the capacitance value of the mutualcapacitance formed between the conductive film C1 and the conductivefilm C2 is reduced. As a result, the value of current flowing from thesignal line ML1 to the signal line ML2 is reduced due to the influenceof an object such as a finger approaching the input device.

The sensor circuit DC2 has a function of sensing the amount of currentthat changes in accordance with the capacitance value of the mutualcapacitance formed between the conductive film C1 and the conductivefilm C2. For example, the value of current flowing in the mutualcapacitance formed between the conductive film C1 and the conductivefilm C2 can be changed by the finger approaching the input device 700TC.Thus, the finger or the like of the user approaching the input devicecan be sensed.

The above-mentioned input device 700TC of one embodiment of the presentinvention includes one conductive film and another conductive filmbetween which an electric field is formed, a driver circuit that selectsthese conductive films in a predetermined order, and a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film. Thus, the object approaching the conductive film can besensed on the basis of a potential that is changed in accordance with anelectric field that is blocked between the plurality of conductive filmsand the search signal. Consequently, a novel input device that is highlyconvenient or reliable can be provided.

Note that the input device 700TC can be used as a mutual capacitivetouch panel.

For example, the input device 700TC can be configured to read a signalusing mutual capacitance formed between some conductive films selectedfrom the plurality of conductive films C and other conductive filmsselected from the plurality of conductive films C. Specifically, asignal may be read by using mutual capacitance formed in the center ornear the center of the selected conductive films.

For example, a plurality of conductive films arranged in the verticaldirection is connected so as to be used as one electrode and a pluralityof conductive films arranged in the horizontal direction is connected soas to be used as the other electrode. The largest mutual capacitance isformed in the vicinity of intersection by the use of the one electrodein which the plurality of conductive films is connected in the verticaldirection and the other electrode in which the plurality of conductivefilms is connected in the horizontal direction. An object such as afinger is easily sensed as the mutual capacitance to be formed islarger; thus, the object such as a finger can be mainly sensed in thevicinity of the intersection.

For example, a signal may be read by the use of mutual capacitancebetween some conductive films selected from the plurality of conductivefilms C and the conductive film C1. In that case, the number ofconductive films not related to sensing of an object such as a fingercan be reduced. As a result, mutual capacitance formed between theconductive films not related to the sensing of an object such as afinger and conductive films related to the sensing of an object such asa finger can be reduced, and the influence of the conductive films notrelated to the sensing can be reduced. Thus, reading sensitivity can beincreased.

For example, a signal may be read by using mutual capacitance formedbetween the conductive film C1 and the conductive film C2 selected fromthe plurality of conductive films C.

Furthermore, the input device 700TC can include the plurality ofconductive films C arranged such that an electric field that is shieldedby an approaching object is formed. Specifically, q conductive films Ccan be arranged in a row direction and p conductive films C can bearranged in a column direction which intersects with the row direction(see FIG. 17A). For example, in the case where the conductive films Care arranged in a matrix of p rows and q columns, p×q conductive films Care provided.

The input device 700TC includes the driver circuit 703C which selectsthe plurality of conductive films C arranged such that an electric fieldthat is shielded by an approaching object is formed. As a specificexample, the input device 700TC includes the driver circuit 703C whichselects a pair of adjacent conductive films C.

<<Structure Example>>

The input device of one embodiment of the present invention includes theconductive film C1, the conductive film C2, the signal line ML1, and thesignal line ML2. The input device of one embodiment of the presentinvention can include the conductive film C (g, h) and the signal lineML (g, h). Note that g is an integer greater than or equal to 1 and lessthan or equal to p, h is an integer greater than or equal to 1 and lessthan or equal to q, and each of p and q is an integer greater than orequal to 1. The input device of one embodiment of the present inventioncan include the driver circuit 703C, the sensor circuit DC2, and thecontrol line CL.

<<Driver Circuit 703C>>

For example, any of a variety of sequential circuits, such as aselection circuit or a shift register, can be used in the driver circuit703C.

Specifically, a shift register that includes a plurality of selectioncircuits and has a function of supplying the selection signals, or thelike may be used in the driver circuit 703C. Accordingly, two or moresignal lines can be selected from the plurality of signal lines in apredetermined order. For example, in the case where six signal lines ML1to ML6 are selected, various selection patterns are provided.

For example, the following pattern is proposed. First, the signal lineML1 and the signal line ML2 are selected; next, the signal line ML3 andthe signal line ML4 are selected; then, the signal line ML5 and thesignal line ML6 are selected.

As another pattern, the signal lines are selected by shifting one byone. For example, the signal line ML1 and the signal line ML2 areselected; then, the signal line ML2 and the signal line ML3 areselected; then, the signal line ML3 and the signal line ML4 areselected; then, the signal line ML4 and the signal line ML5 areselected; and then, the signal line ML5 and the signal line ML6 areselected.

Note that like the conductive film C1 and the conductive film C2, thesignal lines are selected such that the selected conductive films arearranged in the horizontal direction; one embodiment of the presentinvention is not limited to this. The conductive films may be selectedsuch that the selected conductive films are arranged in the verticaldirection.

For example, a transistor can be used for the driver circuit 703C.

<<Sensor Circuit DC2>>

For example, an oscillator circuit, a pulse signal output circuit, acurrent measurement circuit, a peak current measurement circuit, acurrent voltage conversion circuit, an integrator circuit, an ADconversion circuit, or an amplifier circuit can be used for the sensorcircuit DC2.

An oscillator circuit or a pulse signal output circuit capable ofgenerating a square wave, a sawtooth wave, or a triangular wave can beused as the sensor circuit DC2, for example. Accordingly, a signalgenerated from such a circuit can be used as a search signal. That is, asignal needed for reading a signal from a sensor can be output to thesensor when a signal line is selected. Furthermore, whether a finger, apen, or the like approaches a conductive film is sensed by the value ofcurrent flowing at that time, or the like. The sensed result can begiven to an external circuit as a sensing signal. In order to sense thestate of a sensor electrode, a current measurement circuit, a peakcurrent measurement circuit, a current voltage conversion circuit, anintegrator circuit, an AD conversion circuit, or the like is used insome cases. Note that in a period where the signal line ML is notselected, the signal line ML can be brought into a floating state or aconstant voltage can be output to the signal line ML. Note that theconstant voltage corresponds to a common voltage supplied to a displayelement in some cases.

For example, in the case where a potential is sensed, an amplifiercircuit capable of amplifying a change in the potential of the signalline ML (g, h) connected to the amplifier circuit can be used for thesensor circuit DC2. Accordingly, the change in the potential of thesignal line ML (g, h) can be amplified and supplied as a sensing signal.

For example, a first terminal electrically connected to the oscillatorcircuit and a second terminal electrically connected to the amplifiercircuit can be used for the sensor circuit DC2. Accordingly, a generatedsignal can be supplied to the first terminal and an amplified potentialcan be supplied to the second terminal.

Next, an example of the sensor circuit DC2 is described. FIG. 18A showsan example of the case where the sensor circuit DC2 includes the currentmeasurement unit 311 and the pulse signal output circuit 312. Each ofthe current measurement unit 311 and the pulse signal output circuit 312is connected in series between the driver circuit 703C and the groundline 313. Note that a potential supplied to the ground line 313 is notnecessarily 0 V. Furthermore, the current measurement unit 311 and thepulse signal output circuit 312 may be connected to the same wiring, forexample, the ground line 313, or to different wirings.

A pulse signal is output from the pulse signal output circuit 312. Thepulse signal is supplied to the conductive film C (g, h), the conductivefilm C1, the conductive film C2, and the like through the driver circuit703. Then, the amount of current flowing at that time is sensed by thecurrent measurement unit 311.

At this time, in the case where an object such as a finger or a penapproaches the conductive film C (g, h), the conductive film C1, theconductive film C2, and the like, the capacitance value of mutualcapacitance of the conductive film C (g, h), the conductive film C1, theconductive film C2, and the like is reduced. Thus, in the case where anobject such as a finger or a pen approaches, current sensed by thecurrent measurement unit 311 is reduced. That is, the amount of currentis sensed by the current measurement unit 311, whereby touch sensing canbe performed.

Note that as shown in FIG. 18B, a wiring which is brought intoconduction with the driver circuit 703C may be changed with the use of aswitch 318A, a switch 318B, a switch 318C, a switch 318D, or the like sothat the conduction state is changed between the states in FIG. 18A andFIG. 18C.

FIG. 18D shows a specific example of the current measurement unit 311.Here, the current measurement unit 311 includes the capacitor 316 andthe operation amplifier 317. An integrator circuit can be formed withthe use of the operation amplifier 317.

Data sensed by the sensor circuit DC2 is sent to a next circuit.Examples of the next circuit include a memory circuit and a signalprocessing circuit. The next circuit can determine which position istouched. Note that the next circuit may be placed in the sensor circuitDC2.

This embodiment is obtained by performing change, addition,modification, removal, application, superordinate conceptualization, orsubordinate conceptualization on part or the whole of anotherembodiment. Thus, part or the whole of this embodiment can be freelycombined with, applied to, or replaced with part or the whole of any ofthe other embodiments.

Embodiment 4

In this embodiment, a structure of an input/output device of oneembodiment of the present invention is described with reference to FIGS.19A to 19D.

FIGS. 19A to 19D illustrate the structure of an input/output device 700Cof one embodiment of the present invention. FIG. 19A is a block diagramillustrating the structure of the input/output device 700C of oneembodiment of the present invention. FIG. 19B is a block diagramillustrating part of the input/output device 700C in FIG. 19A in detail.FIG. 19C is a cross-sectional view of the input/output device 700C takenalong the section line W1-W2 in FIG. 19B. FIG. 19D is a circuit diagramillustrating the display element 750 (i, j) and a pixel circuit whichcan be used in the pixel 702 (i, j).

Note that the input/output device 700C differs from the input device700TC described with reference to FIGS. 17A to 17C in that a displaydevice is provided. In other words, the input/output device 700C hasportions similar to those of the input device 700TC. Thus, the abovedescription of the input device 700TC can be similarly applied to theinput/output device 700C. Here, the above description is referred to forstructures of the similar portions, and different portions are describedin detail.

<Structure Example 1 of Input/Output Device>

The input/output device 700C described in this embodiment includes thedisplay device and the input device 700TC (see FIG. 19A). That is, theinput/output device 700C has a structure in which the input device 700TCis added to the display device, and specifically, a structure in whichthe input device 700TC is incorporated in part of the display device.Thus, a member functions as part of the display device and alsofunctions as part of the input device 700TC.

The input device 700TC has a function of sensing an object approachingthe display side of the display device (see FIG. 19C).

The display device (output device) includes the pixel 702 (i, j)arranged in a region where the conductive film C1 is provided and thepixel 702 (i, k) arranged in a region where the conductive film C2 isprovided (see FIGS. 19B and 19C).

For example, the pixel 702 (i, j) includes the display element 750 (i,j) and the pixel 702 (i, k) includes the display element 750 (i, k).FIG. 19D illustrates an example of the circuit of the pixel 702 (i, j).

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device, one conductive film configured tobe capacitively coupled to an object approaching a display surface sideof the display device, another conductive film that form an electricfield with the one conductive film, a driver circuit that selects theseconductive films in a predetermined order, and a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film. Thus, the object approaching the display surface sideof the display device can be sensed on the basis of a potential that ischanged in accordance with an electric field that is blocked between theplurality of conductive films and the search signal. Consequently, anovel input/output device that is highly convenient or reliable can beprovided.

The input/output device 700C includes a plurality of pixels (see FIG.19B). For example, the input/output device 700C includes n pixels in thehorizontal direction and m pixels in the vertical direction. That is,the input/output device 700C includes the pixels 702 (i, j) arranged ina matrix of m rows by n columns. Note that i is an integer greater thanor equal to 1 and less than or equal to m, each of j and k is an integergreater than or equal to 1 and less than or equal to n, and each of mand n is an integer greater than or equal to 1. Note that k is differentfrom j.

Furthermore, the pixel 702 (i, j) can have a pixel circuit that drivesthe display element 750 (i, j), and the pixel 702 (i, k) can have apixel circuit that drives the display element 750 (i, k). FIG. 19Dillustrates the pixel circuit of the pixel 702 (i, j). Note that thepixel 702 (i, j) or the pixel 702 (i, k) may include a plurality ofdisplay elements.

In addition, the input/output device 700C can include a scan line G (i)electrically connected to pixels 702 (i, 1) to 702 (i, n) arranged inthe same row.

In addition, the input/output device 700C can include a signal line S(j) electrically connected to pixels 702 (1, j) to 702 (m, j) arrangedin the same column.

Furthermore, the input/output device 700C includes the driver circuit GDelectrically connected to the scan lines G (1) to G (m). The drivercircuit GD has functions of selecting one of the scan lines G (1) to G(m) and supplying a selection signal to the scan lines G (1) to G (m),the pixel 702 (i, j), or the like.

Furthermore, the input/output device 700C includes the driver circuit SDelectrically connected to the signal lines S (1) to S(n). The drivercircuit SD has a function of supplying a video signal to the signallines S (1) to S (n), the pixel 702 (i, j), or the like.

<<Structure Example>>

The input/output device 700C of one embodiment of the present inventionincludes the display device or the input device 700TC.

The input/output device 700C of one embodiment of the present inventionincludes the pixel 702 (i, j) or the pixel 702 (i, k).

The input/output device 700C of one embodiment of the present inventionincludes the pixel element 750 (i, j) or the display element 750 (i, k).

The input/output device 700C of one embodiment of the present inventionincludes the scan line G (i), the signal line S (j), the driver circuitGD, or the driver circuit SD.

<<Input Device>>

As the input/output device 700C of one embodiment of the presentinvention, an input device including the conductive film C1 or theconductive film C2 which is configured to be capacitively coupled to anobject approaching the display surface side of the display device can beused.

For example, a light-transmitting conductive film can be used as theconductive film C1 or the conductive film C2. Alternatively, aconductive film having an opening, a slit, a comb shape, a latticeshape, or the like in a region where the display element is provided canbe used as conductive film C1 or the conductive film C2. Thus, theconductive film C1 or the conductive film C2 can be provided between thedisplay element and a user.

<<Display Device>>

For example, an active matrix display device or a passive matrix displaydevice can be used. Instead of using the display device, a lightingdevice with which a video or an image is not displayed may be used.

<<Display Element 750 (i, j), 750 (i, k)>>

For example, structures that can be used for the display elements 750(i, j) and 750 (i, k) described in Embodiment 2 can be employed.

<<Pixel 702 (i, j), 702 (i, k)>>

For example, the switching element SW, the capacitor Cp, and the likecan be used in the pixel 702 (i, j) or the pixel 702 (i, k). FIG. 19Dshows an example of the pixel 702 (i, j).

Specifically, a transistor can be used as the switching element SW. Forexample, the transistor that can be used in the driver circuit 703described in Embodiment 1 can be used as the switching element SW.

<<Scan Line G (i), Signal Line S (j)>>

For example, structures that can be used for the scan line G (i) and thesignal line S (j) described in Embodiment 2 can be used for those of thescan line G (i) and the signal line S (j) in this embodiment.

<<Driver Circuit GD>>

For example, a structure that can be used for the driver circuit GDdescribed in Embodiment 2 can be used for the driver circuit GD in thisembodiment.

<<Driver Circuit SD>>

For example, a structure that can be used for the driver circuit SDdescribed in Embodiment 2 can be used for the driver circuit SD in thisembodiment.

<Structure Example 2 of Input/Output Device>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIGS. 14A to 14C, FIGS.19A to 19D, and FIG. 20.

Note that the above description is referred to for similar structures,and the structure of using a wiring COM and the structure of usingliquid crystal elements in the pixels 702 (i, j) and (i, k) of thedisplay device are described in detail.

FIG. 20 and FIG. 21 each illustrate a structure of a driver circuit thatcan be used for the input/output device 700C of one embodiment of thepresent invention. FIG. 20 illustrates a structure of the driver circuit703C. FIG. 21 illustrates an example of a structure in which the drivercircuit 703C is used together with a selection circuit MUX.

The input/output device 700C described in this embodiment can includethe wiring COM (see FIG. 19A).

The wiring COM is electrically connected to the driver circuit 703C andhas a function of supplying a predetermined potential.

For example, the driver circuit 703C has a function of letting currentflow between other signal lines ML and the wiring COM in the periodduring which the signal lines ML1 and ML2 are selected.

For example, the driver circuit 703C has a function of preventingcurrent from flowing between each of the signal lines ML1 and ML2 andthe wiring COM in the period during which the signal lines ML1 and ML2are selected. In other words, the driver circuit 703C has a function ofletting current flow between each of the signal lines ML1 and ML2 andthe wiring COM in a period during which other signal lines ML areselected.

For example, the driver circuit 703C has a function of letting currentflow between each of the signal lines ML1 and ML2 and the wiring COM inthe period during which other signal lines ML are selected. In otherwords, the driver circuit 703C has a function of letting current flowbetween each of the signal lines ML1 and ML2 and the wiring COM in aperiod during which the signal lines ML1 and ML2 are not selected.

For example, the driver circuit 703C in FIG. 20 selects the signal lineML1 and the signal line ML2, then selects the signal line ML3 and thesignal line ML4, and then selects the signal line ML5 and the signalline ML6. That is, the driver circuit 703C has a function of selectingsix signal lines ML1 to ML6.

For example, the driver circuit 703C in FIG. 23 selects the signal lineML1 and the signal line ML2, then selects the signal line ML2 and thesignal line ML3, then selects the signal line ML3 and the signal lineML4, then selects the signal line ML4 and the signal line ML5, and thenselects the signal line ML5 and the signal line ML6.

Note that the driver circuit 703C in FIG. 23 includes the shift register301. For example, the shift register 301 controls a plurality ofswitches connected to the signal lines. Note that one embodiment of thepresent invention is not limited thereto. For example, a plurality ofshift registers can be used for the driver circuit 703C. For example,shift registers which independently control switches connected to thesignal lines can be used.

The display element 750 (i, j) includes a layer 753 containing a liquidcrystal material, the conductive film C1, and a pixel electrode 751 (i,j) (see FIGS. 19A and 19B). The pixel electrode 751 (i, j) is providedsuch that an electric field that controls the orientation of the liquidcrystal material is formed between the conductive film C1 and the pixelelectrode 751 (i, j). Note that arrows BL in the drawings show thedirection in which light emitted by a backlight travels.

The display element 750 (i, k) includes the layer 753 containing aliquid crystal material, the conductive film C2, and the pixel electrode751 (i, k). The pixel electrode 751 (i, k) is provided such that anelectric field that controls the orientation of the liquid crystalmaterial can be formed between the conductive film C2 and the pixelelectrode 751 (i, k).

The above-mentioned input/output device of one embodiment of the presentinvention includes a display device including a liquid crystal element,one conductive film configured to control the orientation of the liquidcrystal material and be capacitively coupled to an object approaching adisplay surface side of the display device, another conductive film thatforms an electric field with the one conductive film, a sensor circuitconfigured to supply a search signal to the one conductive film andsupply a sensing signal based on a change in potential of the otherconductive film, and a driver circuit configured to select the oneconductive film and the other conductive film in a predetermined orderand be electrically connected to the sensor circuit or a wiring.

Thus, pixels can be rewritten in a predetermined order, and the objectapproaching the display surface side of the display device including aliquid crystal element can be sensed on the basis of a potential that ischanged in accordance with the search signal and the capacitance coupledto the conductive film. Consequently, a novel input/output device thatis highly convenient or reliable can be provided.

The input/output device 700C includes the base 710 and the base 770including a region overlapping with the base 710 (see FIG. 14B).

The input/output device 700C includes the sealant (not shown) with whichthe base 770 and the base 710 are bonded to each other.

Note that the input/output device 700C includes the layer 753 containinga liquid crystal material in a region surrounded by the base 710, thebase 770, and the sealant.

Individual components included in the input/output device 700C aredescribed below. Note that these components cannot be clearlydistinguished and one component may also serve as another component orinclude part of another component.

For example, the conductive film C2 is a conductive film which isconfigured to be capacitively coupled to an approaching object, and isalso a conductive film arranged such that an electric field is formedbetween the first conductive film and the conductive film C2. Theconductive film C2 is also a common electrode of the display element 750(i, j+1).

<<Structure Example>>

The input/output device of one embodiment of the present inventionincludes the wiring COM in addition to the above-described structure.

The input/output device of one embodiment of the present inventionincludes the layer 753 containing a liquid crystal material and thepixel electrode 751 (i, j) or the pixel electrode 751 (i, k).

<<Wiring COM>>

For example, the structure that can be used for the wiring COM describedin Embodiment 2 can be used for the wiring COM in this embodiment.

<<Driver Circuit 703C>>

For example, the driver circuit 703C can include the shift register 301having a function of supplying a selection signal, or the like (see FIG.20 or FIG. 21).

For example, a selection circuit which has a function of letting currentflow between the sensor circuit DC2 or the wiring COM and the signalline on the basis of the selection signal can be used for the drivercircuit 703C.

Accordingly, with the use of the shift register 301, two selectioncircuits can be sequentially selected from the plurality of selectioncircuits. As a result, current can flow between the signal line ML1electrically connected to one selection circuit to which a selectionsignal is supplied and a first terminal of the sensor circuit DC2. Inaddition, current can flow between the signal line ML2 electricallyconnected to another selection circuit to which a selection signal issupplied and a second terminal of the sensor circuit DC2. In addition,current can flow between a signal line electrically connected to aselection circuit to which a selection signal line is not supplied andthe wiring COM. That is, by the selection signal output from the shiftregister, the conduction state of the switch connected to the signalline ML (g, h) can be controlled. As a result, the conduction statebetween the signal line ML (g, h) and the wiring COM and the conductionstate between the signal line ML (g, h) and the sensor circuit DC2 canbe controlled.

<<Display Element 750 (i, j), 750 (i, k)>>

For example, the structure that can be used for the display element 750(i, j) or the display element 750 (i, k) described in Embodiment 2 canbe used for the display element 750 (i, j) or display element 750 (i, k)in this embodiment.

<Structural Example 3 of Input/Output device>

A structure of the input/output device of one embodiment of the presentinvention is described with reference to FIG. 21. FIG. 21 shows the casewhere the input/output device operates as a touch sensor by switching aself-capacitance mode and a mutual capacitance mode as appropriate, asan example. In such a manner, sensing can be performed more precisely.Alternatively, sensing can be performed in an appropriate mannerdepending on the cases, for example, the case where a finger or the likeis far from an input region or the case where the finger is in contactwith the input region.

Note that the input/output device in FIG. 21 differs from theinput/output device described with reference to FIG. 20 in that theselection circuit MUX electrically connected to the driver circuit 703Cis provided, that the sensor circuit DC11 and the sensor circuit DC12which are electrically connected to the selection circuit MUX areprovided, and that either of the sensor circuits DC11 and DC12 and thesensor circuit DC2 is selected through the selection circuit MUX. Here,the above description is referred to for similar structures, anddifferent structures will be described in detail.

<<Sensor Circuit DC11, DC12>>

For example, the structure that can be used for the sensor circuit DC1described in Embodiment 2 can be used for the sensor circuit DC11 andthe sensor circuit DC12.

<<Selection Circuit MUX>>

The selection circuit MUX has a function of selecting a circuit which isbrought into conduction with the driver circuit 703C, on the basis of acontrol signal. For example, the circuit which is brought intoconduction with the driver circuit 703C is selected on the basis of acontrol signal supplied from the control line CL2.

Specifically, in the case where a selection signal is supplied, theselection circuit MUX has a function of selecting the sensor circuit DC2and letting current flow between the sensor circuit DC2 and the drivercircuit 703C. In the case where another selection signal is supplied,the selection circuit MUX has a function of selecting the sensor circuitDC11 and the sensor circuit DC12 and letting current flow between thedriver circuit 703C and each of the sensor circuit DC11 and the sensorcircuit DC12. For example, in the case where the sensor circuit DC2 isselected, the selection circuit MUX operates in a mutual-capacitancemode; meanwhile, in the case where the sensor circuit DC11 and thesensor circuit DC12 are selected, the selection circuit MUX operates ina self-capacitance mode.

Accordingly, in the case where a selection signal is supplied, currentcan flow between the first terminal of the sensor circuit DC2 and thesignal line ML1 that is selected by the driver circuit 703C and betweenthe second terminal of the sensor circuit DC2 and the signal line ML2.Alternatively, in the case where another selection signal is supplied,current can flow between the sensor circuit DC11 and the signal line ML1that is selected by the driver circuit 703C and between the sensorcircuit DC12 and the signal line ML2 that is selected by the drivercircuit 703C.

FIG. 22 shows a structure example of the selection circuit MUX. AlthoughFIG. 21 shows an example of the case where the selection circuit MUX,the sensor circuit DC11, and the sensor circuit DC12 are applied to thestructure in FIG. 20, one embodiment of the present invention is notlimited to this. For example, the selection circuit MUX, the sensorcircuit DC11, and the sensor circuit DC12 may be applied to thestructure in FIG. 23.

Alternatively, a sensor circuit DC3 which can operate by switching aself-capacitance mode and a mutual-capacitance mode may be provided. Byprovision of such a sensor circuit DC3, the circuit size of the sensorcircuit and the number of elements therein can be reduced. Examples ofsuch a case is shown in FIG. 24 and FIGS. 25A to 25C.

In FIG. 24, the on/off states of switches connected to the signal lineML1, the signal line ML2, the signal line ML3, and the like arecontrolled by a circuit 303. Current flows between the signal line MLwhich does not perform sensing and the wiring COM. Current flows betweenthe signal line ML which performs sensing and the sensor circuit DC3. Atthat time, at least two signal lines ML are selected. Then, the sensorcircuit DC3 operates in accordance with them. Such operation isperformed while the signals lines and pixels are scanned. Thus,operation is performed by switching a self-capacitance mode and amutual-capacitance mode. For example, the circuit 303 includes aplurality of shift register circuits.

FIG. 25A shows an example of the sensor circuit DC3. The on/off statesof switches included in the sensor circuit DC3 are changed, whereby theselection circuit MUX can operate by switching a self-capacitance modeand a mutual-capacitance mode. For example, a circuit structure shown inFIG. 25B is employed in the case of the self-capacitance mode; a circuitstructure shown in FIG. 25C is employed in the case of themutual-capacitance mode. The switches are arranged such that a circuitstructure corresponding to each operation is formed; thus, the circuitstructure of the sensor circuit DC3 is not limited to that shown in FIG.25A.

Consequently, it is possible to provide a novel input/output device withhigh convenience or high reliability, whose structure is switchedbetween the structure of the input/output device 700C described inStructure example 2 of this embodiment and the input/output device 700described in Structure example 3 of this embodiment, on the basis of thecontrol signal supplied from the control line CL2.

This embodiment is obtained by performing change, addition,modification, removal, application, superordinate conceptualization, orsubordinate conceptualization on part or the whole of anotherembodiment. Thus, part or the whole of this embodiment can be freelycombined with, applied to, or replaced with part or the whole of any ofthe other embodiments.

Embodiment 5

In this embodiment, driving methods of an input/output device of oneembodiment of the present invention are described with reference toFIGS. 26A1, 26A2, 26B1, and 26B2.

FIGS. 26A1, 26A2, 26B1, and 26B2 illustrate examples of the drivingmethod of the input/output device of one embodiment of the presentinvention.

FIG. 26A1 is a top view schematically illustrating the input/outputdevice. FIG. 26A2 shows methods for selecting the scan lines G (1) to G(m) and the conductive films C (1, 1) to C (p, q) of the input/outputdevice shown in FIG. 26A1. FIG. 26B1 is a top view schematicallyillustrating the input/output device. FIG. 26B2 shows methods forselecting the scan lines G (1) to G (m) and the conductive films C(1, 1) to C (p, q) of the input/output device shown in FIG. 26B1, whichare different from those described in FIG. 26A2.

<Driving Method 1>

The method of driving the input/output device 700 or the input/outputdevice 700C, which is described in this embodiment, has two periods inone frame period of the display device, for example. Note that themethod may have three or more periods.

The input/output device 700 or the input/output device 700C includes thescan lines G (1) to G (m) (see FIG. 26A1). Furthermore, one frame periodstarts at time 0 and terminates at time T0.

In a first period, the scan lines G (1) to G (m) are sequentiallyselected. Thus, the first period can also be referred to as a videosignal input period or a signal writing period.

For example, in a period T(V) that starts at time 0, the scan lines G(1) to G (m) are sequentially selected. Note that the method ofselecting the scan lines G (1) to G (m) is schematically shown with aline LV (see FIG. 26A2). Pixels in each row are selected and a videosignal is input to the pixels row by row.

For example, in a period T1 shown in the figure, the scan lines G (i) toG (i+x) which are electrically connected to pixels having a regionoverlapping with the conductive films C (g, 1) to C (g, q) aresequentially selected. Furthermore, in the period T1, a predeterminedpotential, e.g., a common potential is applied to the conductive films C(g, 1) to C (g, q).

In a second period, the conductive films C (1, 1) to C (p, q), that is,the signal lines ML (1, 1) to ML (p, q) are sequentially selected. Thus,the second period can also be referred to as a sensing period or asignal reading period.

For example, in a period after the period T(V) in the one frame period,the conductive films C (1, 1) to C (p, q), that is, the signal lines ML(1, 1) to ML (p, q) are sequentially selected. Then, sensing operationis performed on the selected signal line ML (g, h) and the selectedconductive film C (g, h). Note that the method of sequentially selectingthe conductive films C (1, 1) to C (p, q), that is, the signal lines ML(1, 1) to ML (p, q) is schematically shown with a line LS (see FIG.26A2).

Although the case where the conductive films C (1, 1) to C (p, q), thatis, the signal lines ML (1, 1) to ML (p, q) are sequentially selectedone by one is described, one embodiment of the present invention is notlimited to this. For example, they may be sequentially selected two bytwo.

Alternatively, the following method may be performed. When theconductive film C or the signal line ML is selected once, readingoperation in a self-capacitance mode and reading operation in amutual-capacitance mode are sequentially performed; then, the followingconductive film C or the following signal line ML is selected; andreading operation in a self-capacitance mode and reading operation in amutual-capacitance mode are sequentially performed.

Alternatively, the following method may be employed in which reading isperformed in a self-capacitance mode in the first frame and in amutual-capacitance mode in the second frame. Alternatively, thefollowing method may be employed in which reading is performed in aself-capacitance mode for several frame periods in a predeterminedperiod and in a mutual capacitance mode for several frame periods inanother predetermined period.

In these methods, one frame period is divided into at least two periods.That is, the first period in which a video signal is input to a pixel isseparated from the second period in which sensing is performed. Thus, inthe second period, display operation is not affected even when sensingis performed. That is, display operation can be performed continuouslyover one frame period in each pixel. Since the first frame period isdivided into two periods, the speed of scanning the pixel, the signalline ML, or the like is not necessarily the same both in the firstperiod and the second period. For example, in the case where sensingoperation is to be performed with more precision, the second period canbe longer than the first period. On the contrary, in the case whereinput of a video signal is to be performed more precision, the firstperiod can be longer than the second period.

The method of driving the input/output device 700 or the input/outputdevice 700C of one embodiment of the present invention includes a stepof writing image data to the display device and a step of sensing anobject approaching the conductive film of the input/output device. Thus,using the conductive film to which a predetermined potential issupplied, image data can be written into the display device withoutbeing influenced by an approaching finger or the like is inhibited. As aresult, a novel input/output device with high convenience or highreliability can be provided.

<Driving Method 2>

In the method of driving the input/output device 700 or the input/outputdevice 700C which is described in this embodiment, the period in whichinput operation of a video signal is performed and the period in whichsensing operation is performed are not clearly divided in one frameperiod of the display device, and the input operation and the sensingoperation are simultaneously performed. However, in terms of each pixelunit, the input operation of a video signal and the sensing operationare performed in different periods.

Note that the input/output device 700 or the input/output device 700Cincludes the scan lines G (1) to G (m) (see FIG. 26B1). Furthermore, theinput/output device 700 or the input/output device 700C includes pixelswhich are electrically connected to the scan lines G (i) to G (i+x) andlocated in regions overlapping with the conductive films C (g, 1) to C(g, q).

First, in the input operation of a video signal, operation ofsequentially selecting the scan lines G (1) to G (m) is started. First,selection operation is started from the scan line G (1).

Next, after a predetermined time elapsed, that is, before selection ofthe scan lines in all rows is terminated, operation of sequentiallyselecting the conductive films C (1, 1) to C (p, q), that is, the signallines ML (1, 1) to ML (p, q) is started (FIG. 26B2).

At that time, the speed of scanning the pixel, that is, the scan line Gis set to be the same as the speed of scanning the signal line ML or theconductive film C (g, h). That is, when focusing on a pixel, the scanline G is selected first; then, a video signal is input. After the inputof the video signal is terminated, the signal ML is selected after apredetermined time elapsed, and the sensing operation is performed.Here, the conductive film C (g, h) is arranged over a plurality ofpixels. Thus, in accordance with arrangement of the plurality of pixels,timing of selecting the signal line ML needs to be delayed.

For example, in a period T2, the scan lines G (i) to G (i+x) areselected and a video signal is input to the pixels. In that case, in theperiod T2, the conductive films C (g, 1) to C (g, q), that is, thesignal lines ML (g, 1) to ML (g, q) are not selected. That is, after theperiod T2 is terminated, the signal lines ML (g, 1) to ML (g, q) areselected. As described above, operation is performed in such a mannerthat in all the pixels, the scan line G is selected first; then, after apredetermined time elapsed, the signal line ML is selected.Consequently, in terms of each pixel unit, the input operation of avideo signal and the sensing operation do not overlap with each otherand are performed in different periods.

As described above, in terms of each pixel unit, the input operation ofa video signal and the sensing operation do not overlap; thus, thedisplay operation is not affected by the sensing operation. That is, ineach pixel, the display operation can be continuously performed over oneframe period. Furthermore, it is not necessary that the one frame periodbe divided into a plurality of period; thus, the speed of scanning forselecting each pixel can be decreased. Thus, power consumption can bereduced.

The method of driving the input/output device 700 or the input/outputdevice 700C of one embodiment of the present invention includes a stepof writing an image data to a pixel having a region overlapping with apredetermined conductive film and a step of sensing an objectapproaching the predetermined conductive film. Thus, using theconductive film to which a predetermined potential is supplied, imagedata can be written into the display device while influence of anapproaching finger or the like is inhibited. As a result, a novelinput/output device with high convenience or high reliability can beprovided.

This embodiment is obtained by performing change, addition,modification, removal, application, superordinate conceptualization, orsubordinate conceptualization on part or the whole of anotherembodiment. Thus, part or the whole of this embodiment can be freelycombined with, applied to, or replaced with part or the whole of any ofthe other embodiments.

Embodiment 6

In this embodiment, a structure of the input/output device of oneembodiment of the present invention is described with reference to FIGS.27A and 27B and FIGS. 28A to 28C.

FIGS. 27A and 27B illustrate a structure of an input/output device 700Dof one embodiment of the present invention. FIG. 27A is a top view ofthe input/output device 700D of one embodiment of the present inventionand FIG. 27B is a top view of the pixel 702 (i, j) of the input/outputdevice 700D.

FIGS. 28A to 28C illustrate a structure of the input/output device 700Dof one embodiment of the present invention. FIG. 28A is across-sectional view of the input/output device 700D taken along thesection lines X1-X2, X3-X4, and X5-X6 in FIG. 27A. FIG. 28B is across-sectional view illustrating the details of a transistor MD whichis illustrated in FIG. 28A. FIG. 28C is a cross-sectional viewillustrating the details of a transistor MA which is illustrated in FIG.28A.

<Structure Example of Input/Output Device 700D>

The input/output device 700D described in this embodiment includes thebase 710, the base 770, the pixel 702 (i, j), a sealant 730, and aconductive film CD (g, h) (see FIGS. 28A to 28C).

The base 770 has a region overlapping with the base 710. The sealant 730has a function of bonding the base 710 and the base 770.

The pixel 702 (i, j) is provided between the base 710 and the base 770.

The conductive film CD (g, h) is provided between the base 710 and thebase 770.

The pixel 702 (i, j) includes the display element 750.

The display element 750 includes the layer 753 containing a liquidcrystal material and the pixel electrode 751. The pixel electrode 751 isprovided such that an electric field that controls the orientation ofthe liquid crystal material is formed between the conductive film CD (g,h) and the pixel electrode 751.

The layer 753 containing a liquid crystal material is provided in aregion surrounded by the base 710, the base 770, and the sealant 730.

In addition, the input/output device 700D includes a transistor MAelectrically connected to the display element 750. The pixel electrode751 is electrically connected to a source electrode or a drain electrodeof the transistor MA.

The input/output device 700D includes the scan line G (i) electricallyconnected to the transistor MA and the signal line S (j) electricallyconnected to the transistor MA (see FIG. 27B).

In addition, the input/output device 700D includes a plurality oftransistors electrically connected to the scan line G (i) and aplurality of transistors electrically connected to the signal line S(j)(see FIG. 27B).

Specifically, a conductive film 704 serving as a gate electrode of thetransistor MA is electrically connected to the scan line G (i), and aconductive film 712B serving as a source electrode or a drain electrodeof the transistor MA is electrically connected to the signal line S (j)(see FIG. 28C).

A semiconductor film 718 of the input/output device 700D containsindium, gallium, zinc, and oxide.

The conductive film CD (g, h) of the input/output device 700D containsindium, gallium, zinc, and oxide.

The input/output device 700D described in this embodiment includes thetransistor MA which includes the semiconductor film 718 containingindium, gallium, zinc, and oxygen and the conductive film CD (g, h)containing indium, gallium, zinc, and oxygen. Thus, the films containingindium, gallium, zinc, and oxygen can be formed in the same process.Moreover, the films containing indium, gallium, zinc, and oxygen whichare formed in the same process can be used as the semiconductor film orthe conductive film. As a result, a novel input/output device with highconvenience or high reliability can be provided.

The input/output device 700D can include the driver circuit GD or thedriver circuit SD other than the above components (see FIG. 27A).

The driver circuit GD is electrically connected to the scan line G (i)and has a function of supplying a selection signal, for example. Thedriver circuit SD is electrically connected to the signal line S (j) andhas a function of supplying a video signal, for example. For example,the transistor MD can be used in the driver circuit GD. A semiconductorfilm that is formed in the same process as the semiconductor film of thetransistor MA can be used in the transistor MD (see FIGS. 28A to 28C).

The input/output device 700D can include the conductive films CD (g, h)in a matrix of p rows and q columns.

The input/output device 700D can include one or more pixels 702 (i, j)having a region overlapping with the conductive films CD (g, h).

The input/output device 700D can include the pixel electrode 751 whichis provided so that an electric field in a direction intersecting withthe thickness direction of the layer 753 containing a liquid crystalmaterial (such an electric field is also referred to as a horizontalelectric field) is applied.

Components included in the input/output device 700D of one embodiment ofthe present invention are described below. Note that these componentscannot be clearly distinguished and one component may also serve asanother component or include part of another component.

For example, the conductive film C (g, h) is a conductive filmconfigured to be capacitively coupled to an approaching object and alsoserves as a common electrode of the display element 750 (i, j).

The input/output device 700D can include a structure KB between the base710 and the base 770. Accordingly, a predetermined space can be providedbetween the base 710 and the base 770.

The input/output device 700D can include a coloring film CF which has aregion overlapping with the display element 750. Furthermore, theinput/output device 700D can include a light-blocking film BM having anopening in a region overlapping with the display element 750.

The input/output device 700D can include an insulating film 771 betweenthe coloring film CF and the layer 753 containing a liquid crystalmaterial and between the light-blocking film BM and the layer 753containing a liquid crystal material. Thus, unevenness due to thethickness of the coloring film CF can be reduced, or impurities can beprevented from being diffused from the coloring film CF or thelight-blocking film BM to the layer 753 containing a liquid crystalmaterial.

The input/output device 700D can include an alignment film AF1 betweenthe layer 753 containing a liquid crystal material and the base 710 andan alignment film AF2 between the layer 753 containing a liquid crystalmaterial and the base 770.

The input/output device 700D can include an optical film 710P or anoptical film 770P. For example, the optical film 710P can be providedsuch that the base 710 lies between the layer 753 containing a liquidcrystal material and the optical film 710P. Alternatively, the opticalfilm 770P can be provided such that the base 770 lies between the layer753 containing a liquid crystal material and the optical film 770P.

The optical films 710P and 770P can be formed using polarizing plates,for example. One of the polarizing plates is provided in a predeterminedpolarization direction with respect to the polarization direction of theother of the plates. Specifically, the two linear polarizing plates areprovided in a cross-Nicol state.

The input/output device 700D can include a conductive film 724 which hasa region overlapping with the semiconductor film 718 of the transistorMD. The conductive film 724 can be formed of a material which can beformed in the same process as the conductive film CD (g, h) (see FIG.28B).

The input/output device 700D can include an insulating film 701 betweenthe transistor MA and the base 710. The input/output device 700D caninclude an insulating film 721B or an insulating film 728 between thelayer 753 containing a liquid crystal material and the semiconductorfilm 718. The input/output device 700D can include an insulating film721A between the insulating film 721B and the semiconductor film 718.

The insulating film 701 has a function of suppressing impurity diffusionfrom the base 710 to the transistor MA. The insulating film 721B or theinsulating film 721A has a function of suppressing impurity diffusion tothe insulating film 718.

For example, the insulating film 728 makes a step due to the transistorMA or the like which overlaps with the insulating film 728 flat.

The input/output device 700D can include an insulating film 706 betweenthe conductive film 704 and the semiconductor film 718. For example, theinsulating film 706 functions as a gate insulating film.

The input/output device 700D can include a wiring 711 which iselectrically connected to the display element 750 or the conductive filmCD (g, h).

The input/output device 700D can include a terminal 719 which iselectrically connected to the wiring 711. For example, a flexibleprinted circuit board FPC can be electrically connected to the terminal719 using a conductive member ACF.

<<Structure>>

The input/output device 700D includes the base 710, the display element750, and the conductive film CD (g, h).

The input/output device 700D includes the insulating film 721B, thelayer 753 containing a liquid crystal material, and the pixel electrode751.

The input/output device 700D includes the transistor MA, thesemiconductor film 718, the scan line G (i), and the signal line S (j).

The input/output device 700D can include the driver circuit GD and thedriver circuit SD.

<<Base 710, 770>>

For example, the base 710 and the base 770 can be formed using amaterial that can be used for the base 710 described in Embodiment 1.

<<Conductive Film 704, 712A, 712B, Wiring 711, Terminal 719>>

The conductive film 704, the conductive film 712A, the conductive film712B, the wiring 711, or the terminal 719 can be formed using aconductive material.

For example, the conductive film 704, the conductive film 712A, theconductive film 712B, the wiring 711, or the terminal 719 can be formedusing a material that can be used for the conductive film C1, theconductive film C2, the conductive film C (g, h), the signal line ML1,the signal line ML2, the signal line ML (g, h), or the control line CLwhich is described in Embodiment 1.

<<Scan Line G (i), Signal Line S (j)>>

The scan line G (i) or the signal line S (j) can be formed using aconductive material. For example, the scan line G (i) or the signal lineS (j) can be formed using a material which can be used for the wiring711.

<<Conductive Film CD (g, h)>>

The conductive film CD (g, h) can be formed using a conductive material.For example, the conductive film CD (g, h) can be formed using amaterial which can be used for the wiring 711.

Furthermore, an oxide semiconductor can be used for the conductive filmCD (g, h). Note that the method of controlling the resistivity of anoxide semiconductor is described later in the end of this embodiment.

<<Insulating Film 701, 706, 721A, 721B, 728, 771>>

For example, an inorganic insulating material, an organic insulatingmaterial, or an insulating composite material containing an inorganicmaterial and an organic material can be used for the insulating film701, the insulating film 706, the insulating film 721A, the insulatingfilm 721B, the insulating film 728, or the insulating film 771.

Specifically, an inorganic oxide film, an inorganic nitride film, aninorganic oxynitride film, or a material obtained by stacking any ofthese films can be used for the insulating film 701, the insulating film706, the insulating film 721A, the insulating film 721B, the insulatingfilm 728, or the insulating film 771. For example, a silicon oxide film,a silicon nitride film, a silicon oxynitride film, or a materialobtained by stacking any of these films can be used.

Specifically, polyester, polyolefin, polyamide, polyimide,polycarbonate, polysiloxane, an acrylic resin, or a stacked or compositematerial including resins selected from these, or the like can be usedfor the insulating film 721A, the insulating film 721B, the insulatingfilm 728, or the insulating film 771. Alternatively, a photosensitivematerial may be used.

The insulating film 771 can be formed of polyimide, epoxy resin, acrylicresin, or the like.

The insulating film 721B can be formed using a hydrogen-containinginsulating film, for example. The resistivity of the oxide semiconductorcan be controlled by the use of the hydrogen-containing insulating filmfor the insulating film 721B in contact with the oxide semiconductor.

For example, the insulating film 721B can be formed of a material whichcauses hydrogen diffusion when being in contact with the oxidesemiconductor formed in the same process as the semiconductor film 718.

Note that the method of controlling the resistivity of an oxidesemiconductor is described later in the end of this embodiment.

<<Display Element 750>>

For example, a display element having a function of controllingtransmission or reflection of light can be used as the display element750. For example, a combined structure of a polarizing plate and aliquid crystal element or a MEMS shutter display element can be used.

Specifically, a liquid crystal element that can be driven by any of thefollowing driving methods can be used: an in-plane switching (IPS) mode,a twisted nematic (TN) mode, a fringe field switching (FFS) mode, anaxially symmetric aligned micro-cell (ASM) mode, an opticallycompensated birefringence (OCB) mode, a ferroelectric liquid crystal(FLC) mode, an antiferroelectric liquid crystal (AFLC) mode, and thelike.

In addition, a liquid crystal element that can be driven by, forexample, a vertical alignment (VA) mode such as a multi-domain verticalalignment (MVA) mode, a patterned vertical alignment (PVA) mode, or anadvanced super V (ASV) mode can be used for the display element 750.

For example, the display element 750 can include the conductive films CD(g, h) and the pixel electrode 751 which are disposed such that anelectric field that controls the orientation of the liquid crystalmaterial contained in the layer 753 containing the liquid crystalmaterial is formed.

<<Layer 753 Containing a Liquid Crystal Material>>

For example, a liquid crystal material which can be used for the layer753 containing a liquid crystal material described in Embodiment 1 canbe used for the layer 753 containing a liquid crystal material in thisembodiment.

<<Pixel Electrode 751>>

The pixel electrode 751 can be formed using a conductive material.

For example, a material that can be used for the wiring 711 can be usedfor the pixel electrode 751.

Specifically, a light-transmitting conductive material can be used forthe pixel electrode 751. For example, a conductive oxide such as indiumoxide, indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide towhich gallium is added can be used. Thus, the pixel electrode 751 cansupply a uniform electric field without shielding the display of thedisplay element 750.

For example, the pixel electrode 751 can have a comb-like shape or arectangular shape.

<<Transistor MA>>

As the transistor MA, a bottom-gate transistor, a top-gate transistor,or the like can be used.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used as the transistor MA. Specifically, a transistor in which anoxide semiconductor is used for the semiconductor film 718 can be usedas the transistor MA.

Thus, a pixel circuit can hold a video signal for a longer time than apixel circuit including a transistor that uses amorphous silicon for asemiconductor film. Specifically, the selection signal can be suppliedat a frequency of lower than 30 Hz, preferably lower than 1 Hz, morepreferably less than once per minute while flickering is suppressed.Consequently, eyestrain on a user of the input/output device can bereduced, and power consumption for driving can be reduced.

The transistor MA includes the semiconductor film 718 and the conductivefilm 704 having a region overlapping with the semiconductor film 718(see FIG. 28B). The transistor MA further includes the conductive film712A and the conductive film 712B.

Note that the conductive film 704 and the insulating film 706 serve as agate electrode and a gate insulating film, respectively. The conductivefilm 712A serves as one of a source electrode and a drain electrode, andthe conductive film 712B serves as the other of the source electrode andthe drain electrode.

<<Semiconductor Film 718>>

The semiconductor film 718 can be formed using a semiconductorcontaining an element of Group 4, for example. Specifically, asemiconductor containing silicon can be used for the semiconductor film718. For example, single crystal silicon, polysilicon, microcrystallinesilicon, or amorphous silicon can be used for the semiconductor film718.

For example, an oxide semiconductor can be used for the semiconductorfilm 718. Specifically, an oxide semiconductor containing indium or anoxide semiconductor containing indium, gallium, and zinc can be used forthe semiconductor film.

For example, a compound semiconductor can be used for the semiconductorfilm 718. Specifically, a semiconductor containing gallium arsenide canbe used for the semiconductor film 718.

For example, an organic semiconductor can be used for the semiconductorfilm 718. Specifically, an organic semiconductor containing any ofpolyacenes or graphene can be used for the semiconductor film 718.

<<Driver Circuit GD>>

Any of a variety of sequential circuits, such as a shift register, canbe used as the driver circuit GD. For example, the transistor MD, acapacitor, and the like can be used in the driver circuit GD.

For example, a transistor including a semiconductor film that can beformed in the same process as the semiconductor film 718 included in thetransistor MA can be used.

Specifically, as the transistor MD, a transistor having the samestructure as the transistor MA can be used. Alternatively, as thetransistor MD, a transistor different from the transistor MA can beused.

Specifically, a transistor including the conductive film 724 which has aregion overlapping with the conductive film 704 serving as a first gateelectrode can be used as the transistor MD.

The transistor MD includes a stacked-layer of the insulating film 721Aand the insulating film 721B between the conductive film 724 and thesemiconductor film 718.

For example, the conductive film 724 is electrically connected to awiring supplying the same potential as that supplied to the conductivefilm 704.

<<Driver Circuit SD>>

For example, an integrated circuit can be used in the driver circuit SD.Specifically, an integrated circuit formed over a silicon substrate canbe used.

For example, a chip on glass (COG) method can be used to mount thedriver circuit SD. Specifically, the driver circuit SD can be mounted ona pad which is electrically connected to the signal line S (j), using ananisotropic conductive film

<<Sealant 730>>

For example, an inorganic material, an organic material, a compositematerial of an inorganic material and an organic material, or the likecan be used for the sealant 730.

For example, an organic material such as a thermally fusible resin or acurable resin can be used for the sealant 730.

For the sealant 730, an organic material such as a reactive curableadhesive, a photo-curable adhesive, a thermosetting adhesive, and/or ananaerobic adhesive can be used.

Specifically, an adhesive containing an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, or anethylene vinyl acetate (EVA) resin, or the like can be used for thesealant 730.

<<Coloring Film CF>>

The coloring film CF can be formed using a material transmitting lightof a predetermined color and can thus be used as a color filter, forexample

For example, the coloring film CF can be formed using a materialtransmitting light of blue, green, red, yellow, or white.

<<Light-blocking Film BM>>

The light-blocking film BM can be formed using a material that preventslight transmission and can thus be used as a black matrix, for example.

<<Structure KB>>

For example, an organic material, an inorganic material, or a compositematerial of an organic material and an inorganic material can be usedfor the structure KB. Thus, a predetermined space can be providedbetween components between which the structure KB is provided.

Specifically, for the structure KB, polyester, polyolefin, polyamide,polyimide, polycarbonate, polysiloxane, an acrylic resin, or the like,or a composite material of a plurality of kinds of resins selected fromthese can be used. Alternatively, a photosensitive material may be used.

<<Alignment Film AF1, AF2>>

The alignment films AF1 and AF2 can be formed of polyimide or the like.Specifically, an alignment film formed by rubbing treatment or anoptical alignment technique so that a liquid crystal material hasalignment in a predetermined direction can be used.

<<Optical Film 710P, 770P>>

For example, a polarizing plate, a retardation plate, a diffusing film,an anti-reflective film, a condensing film, or the like can be used asthe optical film 710P or the optical film 770P. Alternatively, apolarizing plate containing a dichromatic pigment can be used as theoptical film 710P or the optical film 770P.

Alternatively, an antistatic film preventing the attachment of a foreignsubstance, a water repellent film suppressing the attachment of stain, ahard coat film suppressing a scratch in use, or the like can be used forthe optical film 710P or the optical film 770P.

<Structure Example of Input/Output Device 700E>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIGS. 29A and 29B.

FIGS. 29A and 29B illustrate the structure of an input/output device700E of one embodiment of the present invention. FIG. 29A is across-sectional view of the input/output device 700E of one embodimentof the present invention taken along the section lines X1-X2, X3-X4, andX5-X6 in FIG. 27A. FIG. 29B is a cross-sectional view showing the detailof a transistor MDB shown in FIG. 29A.

Note that the input/output device 700E differs from the input/outputdevice 700D in FIGS. 28A to 28C in that a conductive film 724B isprovided instead of the conductive film 724 (see FIG. 29B) and that aconductive film CE (g, h) is provided instead of the conductive film CD(g, h) (see FIG. 29A). Here, the above description is referred to forsimilar structures, and different structures will be described indetail.

The input/output device 700E described in this embodiment includes theconductive film 724B between the insulating film 721A and the insulatingfilm 721B and includes the conductive film CE (g, h) between theinsulating film 721A and the insulating film 721B. The conductive film724B and the conductive film CE (g, h) contain conductive oxides (seeFIG. 29A or 29B).

<<Conductive Film 724B, Conductive Film CE (g, h)>>

Specifically, an oxide semiconductor whose conductivity is increasedusing a method of controlling the resistivity thereof can be used forthe conductive film 724B and the conductive film CE (g, h).

Specifically, a conductive oxide, such as an indium oxide, indium tinoxide, indium zinc oxide, an oxide containing indium, gallium, and zinc,a zinc oxide, or a zinc oxide to which gallium is added, can be used forthe conductive film 724B and the conductive film CE (g, h).

For example, an oxide semiconductor can be used for each of theconductive film 724B and the conductive film CE (g, h), and ahydrogen-diffusing material can be used for each of the conductive film724B and the insulating film 721B which is in contact with theconductive film CE (g, h). Thus, the resistivity of the conductive film724B and that of the conductive film CE (g, h) can be lowered.

Note that the method of controlling the resistivity of an oxidesemiconductor is described later in the end of this embodiment.

<Structure Example of Input/Output Device 700F>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIGS. 30A and 30B.

FIGS. 30A and 30B illustrate a structure of an input/output device 700Fof one embodiment of the present invention. FIG. 30A is across-sectional view of the input/output device 700F taken along thesection lines X1-X2, X3-X4, and X5-X6 in FIG. 27A. FIG. 30B is across-sectional view showing the details of a transistor MDC in FIG.30A.

Note that the input/output device 700F is different from theinput/output device 700D in FIGS. 28A to 28C in that a top-gatetransistor MC is included instead of the bottom-gate transistor MA, thatthe top-gate transistor MDC is included instead of the bottom-gatetransistor MD, and that a conductive film CF (g, h) is included insteadof the conductive film CD (g, h) (see FIG. 30A). Here, the abovedescription is referred to for similar structures, and differentstructures will be described in detail.

<<Transistor MC, and Transistor MDC>>

The transistor MDC includes the conductive film 704 having a regionoverlapping with an insulating film 701C and the semiconductor film 718having a region provided between the insulating film 701C and theconductive film 704. Note that the conductive film 704 functions as agate electrode (see FIG. 30B).

The semiconductor film 718 includes a first region 718A, a second region718B, and a third region 718C. The first region 718A and the secondregion 718B do not overlap with the conductive film 704. The thirdregion 718C is positioned between the first region 718A and the secondregion 718B and overlaps with the conductive film 704.

The transistor MDC includes the insulating film 706 between the thirdregion 718C and the conductive film 704. Note that the insulating film706 functions as a gate insulating film.

The first region 718A and the second region 718B have a lower resistancethan the third region 718C, and function as a source region and a drainregion.

Note that, for example, a method of controlling the resistivity of theoxide semiconductor film, which is described in the end of thisembodiment, can be used as a method of forming the first region 718A andthe second region 718B in the semiconductor film 718. Specifically,plasma treatment using a gas containing a rare gas can be used.

For example, the conductive film 704 can be a used as a mask. In thatcase, the shape of part of the third region 718C can be self-alignedwith the shape of an end of the conductive film 704.

The transistor MDC includes the conductive films 712A and 712B which arein contact with the first region 718A and the second region 718B,respectively. The conductive film 712A and the conductive film 712Bfunction as a source electrode and a drain electrode.

A transistor which can be formed in the same process as the transistorMDC can be used as the transistor MC.

<<Conductive Film CF (g, h)>>

For example, an oxide semiconductor which is formed in the same processas the first region 718A and the second region 718B of the semiconductorfilm 718 can be used for the conductive film CF (g, h). Accordingly, themanufacturing process of the conductive film CF (g, h) can besimplified.

<Structure Example of Input/Output Device 700G>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIGS. 31A to 31D.

FIGS. 31A to 31D illustrate the structure of an input/output device 700Gof one embodiment of the present invention. FIG. 31A is across-sectional view of the input/output device 700G of one embodimentof the present invention taken along the section lines X1-X2, X3-X4, andX5-X6 in FIG. 27A. FIGS. 31B to 31D are cross-sectional views showingmodification examples where some components shown in FIG. 31A arechanged.

Note that the input/output device 700G differs from the input/outputdevice 700F in FIGS. 30A to 30C in that an insulating film 728B isprovided between the layer 753 containing a liquid crystal material andan insulating film 728A, and that a conductive film CG (g, h) isprovided between the insulating film 728A and the insulating film 728Binstead of the conductive film CF (g, h). Here, the above description isreferred to for similar structures, and different structures will bedescribed in detail.

The input/output device 700G includes the insulating film 728B betweenthe layer 753 containing a liquid crystal material and the insulatingfilm 728A. The input/output device 700G includes the conductive film CG(g, h) between the insulating film 728A and the insulating film 728B.

<<Insulating Film 728A>>

For example, the material that can be used for the insulating film 728can be used for the insulating film 728A.

<<Insulating Film 728B>>

For example, the material that can be used for the insulating film 728can be used for the insulating film 728B.

<<Conductive Film CG (g, h)>>

For example, a conductive film having an opening in a region overlappingwith the comb-like pixel electrode 751 can be used as the conductivefilm CG (g, h).

For example, a conductive material can be used for the conductive filmCG (g, h). For example, the material that can be used for or the wiring711 can be used for the conductive film CG (g, h).

Specifically, a light-transmitting conductive material can be used forthe conductive film CG (g, h).

For example, a conductive oxide such as indium oxide, indium tin oxide,indium zinc oxide, zinc oxide, or zinc oxide to which gallium is addedcan be used. Thus, the conductive film CG (g, h) can supply a uniformelectric field without shielding the display of the display element 750.

Note that a conductive film overlapping with the pixel electrode 751 andthe opening of the pixel electrode 751 can be used as the conductivefilm CG (g, h) (see FIG. 31B).

Alternatively, a conductive film which can be provided in the opening ofthe pixel electrode 751 can be used as the conductive film CG (g, h)(see FIG. 31C).

Alternatively, a conductive film having an opening and an a non-openingportion which overlap with part of the pixel electrode 751 can be usedas the conductive film CG (g, h) (see FIG. 31D).

<Structure Example of Input/Output Device 700H>

Another structure of the input/output device of one embodiment of thepresent invention is described with reference to FIGS. 32A and 32B.

FIGS. 32A and 32B illustrate the structure of an input/output device700H of one embodiment of the present invention. FIG. 32A is across-sectional view of the input/output device 700H taken along thesection lines X1-X2, X3-X4, and X5-X6 in FIG. 27A. FIG. 32B is across-sectional view illustrating the details of a transistor MDE whichis illustrated in FIG. 32A.

Note that the input/output device 700H differs from the input/outputdevice 700D described with reference to FIGS. 28A to 28C in that achannel protective transistor ME is provided instead of the channeletched transistor MA, that a channel protective transistor MDE isprovided instead of the channel etched transistor MD, that the coloringfilm CF is provided between the conductive film CD (g, h) and the pixelelectrode 751, and that the light-blocking film BM is provided betweenthe layer 753 containing a liquid crystal material and the base 710 (seeFIG. 32A). Here, the above description is referred to for similarstructures, and different structures will be described in detail.

<<Transistor ME, Transistor MDE>>

The transistors ME and MDE can be channel protective transistors. Forexample, the transistor MDE includes the insulating film 721A which isprovided so that the semiconductor film 718 is sandwiched between theinsulating film 721A and the insulating film 706 serving as a gateinsulating film (see FIG. 32B).

<Method of Controlling Resistivity of Oxide Semiconductor>

The method of controlling the resistivity of a film containing oxidesemiconductor will be described.

A film containing an oxide semiconductor with a predeterminedresistivity can be used for the conductive film CD (g, h) (see FIG.28A), the conductive film CE (g, h), and the conductive film 724B (seeFIGS. 29A and 29B), or the conductive film CF (g, h), the first region718A, and the second region 718B (see FIGS. 30A and 30B).

For example, a method of controlling the concentration of impuritiessuch as hydrogen and water contained in the oxide semiconductor and/orthe oxygen vacancies in the film can be used as the method ofcontrolling the resistivity of an oxide semiconductor film.

Specifically, plasma treatment can be used as a method of increasing ordecreasing the concentration of impurities such as hydrogen and waterand/or the oxygen vacancies in the film.

Specifically, plasma treatment using a gas containing one or more kindsselected from a rare gas (He, Ne, Ar, Kr, or Xe), hydrogen, boron,phosphorus, and nitrogen can be employed. For example, plasma treatmentin an Ar atmosphere, plasma treatment in a mixed gas atmosphere of Arand hydrogen, plasma treatment in an ammonia atmosphere, plasmatreatment in a mixed gas atmosphere of Ar and ammonia, or plasmatreatment in a nitrogen atmosphere can be employed. Thus, the oxidesemiconductor film can have a high carrier density and a lowresistivity.

Alternatively, hydrogen, boron, phosphorus, or nitrogen is added to theoxide semiconductor film by an ion implantation method, an ion dopingmethod, a plasma immersion ion implantation method, or the like, so thatthe oxide semiconductor film can have a low resistivity.

Alternatively, a method in which an insulating film containing hydrogenis formed in contact with the oxide semiconductor film, and the hydrogenis diffused from the insulating film to the oxide semiconductor film canbe used. Thus, the oxide semiconductor film can have a high carrierdensity and a low resistivity.

For example, an insulating film with a hydrogen concentration of greaterthan or equal to 1×10²² atoms/cm³ is formed in contact with the oxidesemiconductor film, in which case hydrogen can be effectively suppliedto the oxide semiconductor film. Specifically, a silicon nitride filmcan be used as the insulating film formed in contact with the oxidesemiconductor film.

Hydrogen contained in the oxide semiconductor film reacts with oxygenbonded to a metal atom to form water, and also causes oxygen vacanciesin a lattice from which oxygen is released (or a portion from whichoxygen is released). Entry of hydrogen into the oxygen vacancy generatesan electron serving as a carrier in some cases. Furthermore, in somecases, bonding of part of hydrogen to oxygen bonded to a metal atomcauses generation of an electron serving as a carrier. Thus, the oxidesemiconductor film can have a high carrier density and a lowresistivity.

Specifically, an oxide semiconductor with a hydrogen concentrationmeasured by secondary ion mass spectrometry (SIMS) of greater than orequal to 8×10¹⁹ atoms/cm³, preferably greater than or equal to 1×10²⁰atoms/cm³, more preferably greater than or equal to 5×10²⁰ atoms/cm³ canbe suitably used for the conductive film CD (g, h) (see FIG. 28A), theconductive film CE (g, h) and the conductive film 724B (see FIGS. 29Aand 29B), or the second conductive film CF (g, h), the first region 718Aand the second region 718B (see FIGS. 30A and 30B).

Meanwhile, an oxide semiconductor with a high resistivity can be usedfor a semiconductor film where a channel of a transistor is formed.

For example, an insulating film containing oxygen, in other words, aninsulating film capable of releasing oxygen, is formed in contact withan oxide semiconductor film, and the oxygen is supplied from theinsulating film to the oxide semiconductor film, so that oxygenvacancies in the film or at the interface can be filled. Thus, the oxidesemiconductor film can have a high resistivity.

For example, a silicon oxide film or a silicon oxynitride film can beused as the insulating film capable of releasing oxygen.

The oxide semiconductor film in which oxygen vacancies are compensatedwith oxygen and the hydrogen concentration is reduced can be referred toas a highly purified intrinsic or substantially highly purifiedintrinsic oxide semiconductor film. Here, the term “substantiallyintrinsic” refers to a state where an oxide semiconductor film has acarrier density of lower than 8×10¹¹/cm³, preferably lower than1×10¹¹/cm³, more preferably lower than 1×10¹⁰/cm³. A highly purifiedintrinsic or substantially highly purified intrinsic oxide semiconductorfilm has few carrier generation sources, and thus can have a low carrierdensity. The highly purified intrinsic or substantially highly purifiedintrinsic oxide semiconductor film has a low density of defect statesand can accordingly have a low density of trap states.

Furthermore, a transistor including the highly purified intrinsic orsubstantially highly purified intrinsic oxide semiconductor film has anextremely low off-state current; even when an element has a channelwidth of 1×10⁶ μm and a channel length L of 10 μm, the off-state currentcan be lower than or equal to the measurement limit of a semiconductorparameter analyzer, that is, lower than or equal to 1×10⁻¹³ A, at avoltage (drain voltage) between a source electrode and a drain electrodeof from 1 V to 10 V.

The transistor in which a channel region is formed in the oxidesemiconductor film that is a highly purified intrinsic or substantiallyhighly purified intrinsic oxide semiconductor film can have a smallchange in electrical characteristics and high reliability.

Specifically, an oxide semiconductor whose hydrogen concentrationmeasured by secondary ion mass spectrometry (SIMS) is lower than orequal to 2×10²⁰ atoms/cm³, preferably lower than or equal to 5×10¹⁹atoms/cm³, more preferably lower than or equal to 1×10¹⁹ atoms/cm³, morepreferably lower than 5×10¹⁸ atoms/cm³, more preferably lower than orequal to 1×10¹⁸ atoms/cm³, more preferably lower than or equal to 5×10¹⁷atoms/cm³, more preferably lower than or equal to 1×10¹⁶ atoms/cm³ canbe favorably used for a semiconductor film where a channel of atransistor is formed.

Note that the transistor MDB includes the semiconductor film 718 and anoxide semiconductor film that has a higher hydrogen concentration and/ora larger number of oxygen vacancies and that has a lower resistivitythan the semiconductor film 718 can be used as the conductive film 724B(see FIG. 29B).

The hydrogen concentration in the conductive film 724B is twice or more,preferably ten times or more that in the semiconductor film 718.

The resistivity of the conductive film 724B is greater than or equal to1×10⁻⁸ times and less than 1×10⁻¹ times that of the semiconductor film718.

Specifically, the resistivity of the conductive film 724B is higher thanor equal to 1×10⁻³ Ωcm and lower than 1×10⁴ Ωcm, preferably higher thanor equal to 1×10⁻³ Ωcm and lower than 1×10⁻¹ Ωcm.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 7

In this embodiment, the input/output device of one embodiment of thepresent invention or structures of a transistor that can be used in theinput/output device of one embodiment of the present invention will bedescribed with reference to FIGS. 33A to 33D.

<Structure Example of Semiconductor Device>

FIG. 33A is a top view of a transistor 100. FIG. 33C is across-sectional view taken along the section line X1-X2 in FIG. 33A, andFIG. 33D is a cross-sectional view taken along the section line Y1-Y2 inFIG. 33A. Note that in FIG. 33A, some components of the transistor 100(e.g., an insulating film functioning as a gate insulating film) are notillustrated to avoid complexity. Furthermore, the direction of thesection line X1-X2 may be called a channel length direction, and thedirection of the section line Y1-Y2 may be called a channel widthdirection. As in FIG. 33A, some components are not illustrated in somecases in top views of transistors described below.

The transistor 100 can be used for the input/output device 700Ddescribed in Embodiment 6.

For example, when the transistor 100 is used as the transistor MA, asubstrate 102, a conductive film 104, a stacked film of insulating films106 and 107, an oxide semiconductor film 108, a conductive film 112 a, aconductive film 112 b, a stacked film of insulating films 114 and 116,and an insulating film 118 can be referred to as the insulating film701C, the conductive film 704, the insulating film 706, thesemiconductor film 708, the conductive film 712A, the conductive film712B, the insulating film 716, and an insulating film 721B,respectively.

The transistor 100 includes the conductive film 104 functioning as agate electrode over the substrate 102, the insulating film 106 over thesubstrate 102 and the conductive film 104, the insulating film 107 overthe insulating film 106, the oxide semiconductor film 108 over theinsulating film 107, and the conductive film 112 a and the conductivefilm 112 b functioning as a source electrode and a drain electrode,respectively, electrically connected to the oxide semiconductor film108. Over the transistor 100, specifically, over the conductive films112 a and 112 b and the oxide semiconductor film 108, insulating films114, 116, and 118 are provided. The insulating films 114, 116, and 118function as protective insulating films for the transistor 100.

The oxide semiconductor film 108 includes a first oxide semiconductorfilm 108 a on the conductive film 104 (functioning as a gate electrode)side and a second oxide semiconductor film 108 b over the first oxidesemiconductor film 108 a. The insulating films 106 and 107 function asgate insulating films of the transistor 100.

In—M oxide (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf) or In—M—Zn oxidecan be used for the oxide semiconductor film 108. It is particularlypreferable to use In—M—Zn oxide for the oxide semiconductor film 108.

The first oxide semiconductor film 108 a includes a first region inwhich the atomic proportion of In is larger than the atomic proportionof M. The second oxide semiconductor film 108 b includes a second regionin which the atomic proportion of In is smaller than that in the firstoxide semiconductor film 108 a. The second region includes a portionthinner than the first region.

The first oxide semiconductor film 108 a including the first region inwhich the atomic proportion of In is larger than that of M can increasethe field-effect mobility (also simply referred to as mobility or μFE)of the transistor 100. Specifically, the field-effect mobility of thetransistor 100 can exceed 10 cm²/Vs.

For example, the use of the transistor with high field-effect mobilityfor a gate driver that generates a gate signal (specifically, ademultiplexer connected to an output terminal of a shift registerincluded in a gate driver) allows a semiconductor device or a displaydevice to have a narrow frame.

On the other hand, the first oxide semiconductor film 108 a includingthe first region in which the atomic proportion of In is larger thanthat of M makes it easier to change electrical characteristics of thetransistor 100 in light irradiation. However, in the semiconductordevice of one embodiment of the present invention, the second oxidesemiconductor film 108 b is formed over the first oxide semiconductorfilm 108 a. In addition, the thickness of the channel region in thesecond oxide semiconductor film 108 b is less than the thickness of thefirst oxide semiconductor film 108 a.

Furthermore, the second oxide semiconductor film 108 b includes thesecond region in which the atomic proportion of In is smaller than thefirst oxide semiconductor film 108 a and thus has larger Eg than that ofthe first oxide semiconductor film 108 a. For this reason, the oxidesemiconductor film 108 which is a stacked-layer structure of the firstoxide semiconductor film 108 a and the second oxide semiconductor film108 b has high resistance to a negative bias stress test with lightirradiation.

The amount of light absorbed by the oxide semiconductor film 108 withthe above structure can be reduced during light irradiation. As aresult, the change in electrical characteristics of the transistor 100due to light irradiation can be reduced. In the semiconductor device ofone embodiment of the present invention, the insulating film 114 or theinsulating film 116 includes excess oxygen. This structure can furtherreduce the change in electrical characteristics of the transistor 100due to light irradiation.

Here, the oxide semiconductor film 108 is described in detail withreference to FIG. 33B.

FIG. 33B is a cross-sectional enlarged view of the oxide semiconductorfilm 108 and the vicinity thereof in the transistor 100 illustrated inFIG. 33C.

In FIG. 33B, t1, t2-1, and t2-2 denote a thickness of the first oxidesemiconductor film 108 a, one thickness of the second oxidesemiconductor film 108 b, and the other thickness of the second oxidesemiconductor film 108 b, respectively. The second oxide semiconductorfilm 108 b over the first oxide semiconductor film 108 a prevents thefirst oxide semiconductor film 108 a from being exposed to an etchinggas, an etchant, or the like when the conductive films 112 a and 112 bare formed. This is why the first oxide semiconductor film 108 a is notor is hardly reduced in thickness. In contrast, in the second oxidesemiconductor film 108 b, a portion not overlapping with the conductivefilms 112 a and 112 b is etched by formation of the conductive films 112a and 112 b, so that a depression is formed in the etched region. Inother words, a thickness of the second oxide semiconductor film 108 b ina region overlapping with the conductive films 112 a and 112 b is t2-1,and a thickness of the second oxide semiconductor film 108 b in a regionnot overlapping with the conductive films 112 a and 112 b is t2-2.

As for the relationships between the thicknesses of the first oxidesemiconductor film 108 a and the second oxide semiconductor film 108 b,t2-1>t1>t2-2 is preferable. A transistor with the thicknessrelationships can have high field-effect mobility and less variation inthreshold voltage in light irradiation.

When oxygen vacancy is formed in the oxide semiconductor film 108included in the transistor 100, electrons serving as carriers aregenerated; as a result, the transistor 100 tends to be normally-on.Therefore, for stable transistor characteristics, it is important toreduce oxygen vacancy in the oxide semiconductor film 108 particularlyoxygen vacancy in the first oxide semiconductor film 108 a. In thestructure of the transistor of one embodiment of the present invention,excess oxygen is introduced into an insulating film over the oxidesemiconductor film 108, here, the insulating film 114 and/or theinsulating film 116 over the oxide semiconductor film 108, wherebyoxygen is moved from the insulating film 114 and/or the insulating film116 to the oxide semiconductor film 108 to fill oxygen vacancy in theoxide semiconductor film 108 particularly in the first oxidesemiconductor film 108 a.

It is preferable that the insulating films 114 and 116 each include aregion (oxygen excess region) including oxygen in excess of that in thestoichiometric composition. In other words, the insulating films 114 and116 are insulating films capable of releasing oxygen. Note that theoxygen excess region is formed in the insulating films 114 and 116 insuch a manner that oxygen is introduced into the insulating films 114and 116 after the deposition, for example. As a method for introducingoxygen, an ion implantation method, an ion doping method, a plasmaimmersion ion implantation method, plasma treatment, or the like may beemployed.

In order to fill oxygen vacancy in the first oxide semiconductor film108 a, the thickness of the portion including the channel region and thevicinity of the channel region in the second oxide semiconductor film108 b is preferably small, and t2-2<t1 is preferably satisfied. Forexample, the thickness of the portion including the channel region andthe vicinity of the channel region in the second oxide semiconductorfilm 108 b is preferably greater than or equal to 1 nm and less than orequal to 20 nm and further preferably greater than or equal to 3 nm andless than or equal to 10 nm.

Other constituent elements of the semiconductor device of thisembodiment are described below in detail.

<<Substrate>>

There is no particular limitation on the property of a material and thelike of the substrate 102 as long as the material has heat resistanceenough to withstand at least heat treatment to be performed later. Forexample, a glass substrate, a ceramic substrate, a quartz substrate, ora sapphire substrate may be used as the substrate 102. Alternatively, asingle crystal semiconductor substrate or a polycrystallinesemiconductor substrate of silicon or silicon carbide, a compoundsemiconductor substrate of silicon germanium, an SOI substrate, or thelike can be used as the substrate 102. Alternatively, any of thesesubstrates provided with a semiconductor element may be used as thesubstrate 102. Note that in the case where a glass substrate is used asthe substrate 102, a large substrate having any of the following sizescan be used: the 6th generation (1500 mm×1850 mm), the 7th generation(1870 mm×2200 mm), the 8th generation (2200 mm×2400 mm), the 9thgeneration (2400 mm×2800 mm), and the 10th generation (2950 mm×3400 mm).Thus, a large display device can be manufactured.

Alternatively, a flexible substrate may be used as the substrate 102,and the transistor 100 may be provided directly on the flexiblesubstrate. Alternatively, a separation layer may be provided between thesubstrate 102 and the transistor 100. The separation layer can be usedwhen part or the whole of a semiconductor device formed over theseparation layer is separated from the substrate 102 and transferredonto another substrate. In such a case, the transistor 100 can betransferred to a substrate having low heat resistance or a flexiblesubstrate as well.

<<Conductive Film Functioning as Gate Electrode, Source Electrode, andDrain Electrode>>

The conductive film 104 functioning as a gate electrode, and theconductive film 112 a and the conductive film 112 b functioning as asource electrode and a drain electrode, respectively, each can be formedusing a metal element selected from chromium (Cr), copper (Cu), aluminum(Al), gold (Au), silver (Ag), zinc (Zn), molybdenum (Mo), tantalum (Ta),titanium (Ti), tungsten (W), manganese (Mn), nickel (Ni), iron (Fe), andcobalt (Co); an alloy including any of these metal element as itscomponent; an alloy including a combination of any of these metalelements; or the like.

Furthermore, the conductive films 104, 112 a, and 112 b may have asingle-layer structure or a stacked-layer structure of two or morelayers. For example, a single-layer structure of an aluminum filmincluding silicon, a two-layer structure in which a titanium film isstacked over an aluminum film, a two-layer structure in which a titaniumfilm is stacked over a titanium nitride film, a two-layer structure inwhich a tungsten film is stacked over a titanium nitride film, atwo-layer structure in which a tungsten film is stacked over a tantalumnitride film or a tungsten nitride film, and a three-layer structure inwhich a titanium film, an aluminum film, and a titanium film are stackedin this order can be given. Alternatively, an alloy film or a nitridefilm in which aluminum and one or more elements selected from titanium,tantalum, tungsten, molybdenum, chromium, neodymium, and scandium arecombined may be used.

The conductive films 104, 112 a, and 112 b can be formed using alight-transmitting conductive material such as indium tin oxide, indiumoxide including tungsten oxide, indium zinc oxide including tungstenoxide, indium oxide including titanium oxide, indium tin oxide includingtitanium oxide, indium zinc oxide, or indium tin oxide to which siliconoxide is added.

A Cu—X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) may be usedfor the conductive films 104, 112 a, and 112 b. Use of a Cu—X alloy filmenables the manufacturing cost to be reduced because wet etching processcan be used in the processing.

<<Insulating Film Functioning as Gate Insulating Film>>

As each of the insulating films 106 and 107 functioning as gateinsulating films of the transistor 100, an insulating film including atleast one of the following films formed by a plasma enhanced chemicalvapor deposition (PECVD) method, a sputtering method, or the like can beused: a silicon oxide film, a silicon oxynitride film, a silicon nitrideoxide film, a silicon nitride film, an aluminum oxide film, a hafniumoxide film, an yttrium oxide film, a zirconium oxide film, a galliumoxide film, a tantalum oxide film, a magnesium oxide film, a lanthanumoxide film, a cerium oxide film, and a neodymium oxide film. Note thatinstead of a stacked-layer structure of the insulating films 106 and107, an insulating film of a single layer formed using a materialselected from the above or an insulating film of three or more suchlayers may be used.

The insulating film 106 has a function as a blocking film which inhibitspenetration of oxygen. For example, in the case where excess oxygen issupplied to the insulating film 107, the insulating film 114, theinsulating film 116, and/or the oxide semiconductor film 108, theinsulating film 106 can inhibit penetration of oxygen.

Note that the insulating film 107 that is in contact with the oxidesemiconductor film 108 functioning as a channel region of the transistor100 is preferably an oxide insulating film and preferably includes aregion including oxygen in excess of the stoichiometric composition(oxygen-excess region). In other words, the insulating film 107 is aninsulating film capable of releasing oxygen. In order to provide theoxygen excess region in the insulating film 107, the insulating film 107is formed in an oxygen atmosphere, for example. Alternatively, theoxygen excess region may be formed by introduction of oxygen into theinsulating film 107 after the deposition. As a method for introducingoxygen, an ion implantation method, an ion doping method, a plasmaimmersion ion implantation method, plasma treatment, or the like may beemployed.

In the case where hafnium oxide is used for the insulating film 107, thefollowing effect is attained. Hafnium oxide has a higher dielectricconstant than silicon oxide and silicon oxynitride. Therefore, hafniumoxide, can reduce the leakage current due to tunnel current because theuse of hafnium oxide can increase the thickness of the insulating film107 as compared with the use of silicon oxide. That is, it is possibleto provide a transistor with a low off-state current. Moreover, hafniumoxide with a crystalline structure has a higher dielectric constant thanhafnium oxide with an amorphous structure. Therefore, it is preferableto use hafnium oxide with a crystalline structure in order to provide atransistor with a low off-state current. Examples of the crystallinestructure include a monoclinic crystal structure and a cubic crystalstructure. Note that one embodiment of the present invention is notlimited thereto.

In this embodiment, a silicon nitride film is formed as the insulatingfilm 106, and a silicon oxide film is formed as the insulating film 107.The silicon nitride film has a higher dielectric constant than a siliconoxide film and needs a greater thickness for capacitance equivalent tothat of the silicon oxide film. Thus, when the silicon nitride film isincluded in the gate insulating film of the transistor 100, the physicalthickness of the insulating film can be increased. This makes itpossible to reduce a decrease in withstand voltage of the transistor 100and furthermore to increase the withstand voltage, thereby reducingelectrostatic discharge damage to the transistor 100.

<<Oxide Semiconductor Film>>

The oxide semiconductor film 108 can be formed using the materialsdescribed above.

In the case where the oxide semiconductor film 108 includes In—M—Znoxide, it is preferable that the atomic ratio of metal elements of asputtering target used for forming the In—M—Zn oxide satisfy In≧M andZn≧M As the atomic ratio of metal elements of such a sputtering target,In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=2:1:3, In:M:Zn=3:1:2, andIn:M:Zn=4:2:4.1 are preferable.

In the case where the oxide semiconductor film 108 is formed of In—M—Znoxide, it is preferable to use a target including polycrystallineIn—M—Zn oxide as the sputtering target. The use of the target includingpolycrystalline In—M—Zn oxide facilitates formation of the oxidesemiconductor film 108 having crystallinity. Note that the atomic ratiosof metal elements in the formed oxide semiconductor film 108 vary fromthe above atomic ratio of metal elements of the sputtering target withina range of ±40% as an error. For example, when a sputtering target withan atomic ratio of In to Ga and Zn of 4:2:4.1 is used, the atomic ratioof In to Ga and Zn in the oxide semiconductor film 108 may be 4:2:3 orin the vicinity of 4:2:3.

The first oxide semiconductor film 108 a can be formed using thesputtering target having an atomic ratio of In:M:Zn=2:1:3,In:M:Zn=3:1:2, or In:M:Zn=4:2:4.1, for example. The second oxidesemiconductor film 108 b can be formed using the sputtering targethaving an atomic ratio of In:M:Zn=1:1:1 or In:M:Zn=1:1:1.2, for example.Note that the atomic ratio of metal elements in a sputtering target usedfor forming the second oxide semiconductor film 108 b does notnecessarily satisfy In≧M and Zn≧M, and may satisfy In≧M and Zn<M, suchas In:M:Zn=1:3:2.

The energy gap of the oxide semiconductor film 108 is 2 eV or more,preferably 2.5 eV or more, and further preferably 3 eV or more. The useof an oxide semiconductor having a wide energy gap can reduce off-statecurrent of the transistor 100. In particular, an oxide semiconductorfilm having an energy gap of 2 eV or more, preferably 2 eV or more and3.0 eV or less is preferably used as the first oxide semiconductor film108 a, and an oxide semiconductor film having an energy gap of 2.5 eV ormore and 3.5 eV or less is preferably used as the second oxidesemiconductor film 108 b. Furthermore, the second oxide semiconductorfilm 108 b preferably has a higher energy gap than that of the firstoxide semiconductor film 108 a.

Each thickness of the first oxide semiconductor film 108 a and thesecond oxide semiconductor film 108 b is larger than or equal to 3 nmand smaller than or equal to 200 nm, preferably larger than or equal to3 nm and smaller than or equal to 100 nm and further preferably largerthan or equal to 3 nm and smaller than or equal to 50 nm. Note that theabove-described thickness relationships between them are preferablysatisfied.

An oxide semiconductor film with low carrier density is used as thesecond oxide semiconductor film 108 b. For example, the carrier densityof the second oxide semiconductor film 108 b is lower than or equal to1×10¹⁷/cm³, preferably lower than or equal to 1×10¹⁵/cm³, furtherpreferably lower than or equal to 1×10¹³/cm³, and still furtherpreferably lower than or equal to 1×10¹¹/cm³.

Note that without limitation to the compositions and materials describedabove, a material with an appropriate composition may be used dependingon required semiconductor characteristics and electrical characteristics(e.g., field-effect mobility and threshold voltage) of a transistor.Furthermore, in order to obtain required semiconductor characteristicsof a transistor, it is preferable that the carrier density, the impurityconcentration, the defect density, the atomic ratio of a metal elementto oxygen, the interatomic distance, the density, and the like of thefirst oxide semiconductor film 108 a and the second oxide semiconductorfilm 108 b be set to be appropriate.

Note that it is preferable to use, as the first oxide semiconductor film108 a and the second oxide semiconductor film 108 b, an oxidesemiconductor film in which the impurity concentration is low and thedensity of defect states is low, in which case the transistor can havemore excellent electrical characteristics. Here, the state in which theimpurity concentration is low and the density of defect states is low(the amount of oxygen vacancy is small) is referred to as “highlypurified intrinsic” or “substantially highly purified intrinsic”. Ahighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film has few carrier generation sources, and thuscan have a low carrier density. Thus, a transistor in which a channelregion is formed in the oxide semiconductor film rarely has a negativethreshold voltage (is rarely normally on). A highly purified intrinsicor substantially highly purified intrinsic oxide semiconductor film hasa low density of defect states and accordingly has a low density of trapstates in some cases. Furthermore, the highly purified intrinsic orsubstantially highly purified intrinsic oxide semiconductor film has anextremely low off-state current; even when an element has a channelwidth of 1×10⁶ μm and a channel length of 10 μm, the off-state currentcan be less than or equal to the measurement limit of a semiconductorparameter analyzer, that is, less than or equal to 1×10⁻¹³ A, at avoltage (drain voltage) between a source electrode and a drain electrodeof from 1 V to 10 V.

Accordingly, the transistor in which the channel region is formed in thehighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film can have a small change in electricalcharacteristics and high reliability. Charges trapped by the trap statesin the oxide semiconductor film take a long time to be released and maybehave like fixed charges. Thus, the transistor whose channel region isformed in the oxide semiconductor film having a high density of trapstates has unstable electrical characteristics in some cases. Asexamples of the impurities, hydrogen, nitrogen, alkali metal, alkalineearth metal, and the like are given.

Hydrogen included in the oxide semiconductor film reacts with oxygenbonded to a metal atom to be water, and also causes oxygen vacancy in alattice from which oxygen is released (or a portion from which oxygen isreleased). Due to entry of hydrogen into the oxygen vacancy, an electronserving as a carrier is generated in some cases. Furthermore, in somecases, bonding of part of hydrogen to oxygen bonded to a metal atomcauses generation of an electron serving as a carrier. Thus, atransistor including an oxide semiconductor film which contains hydrogenis likely to be normally on. Accordingly, it is preferable that hydrogenbe reduced as much as possible in the oxide semiconductor film 108.Specifically, in the oxide semiconductor film 108, the concentration ofhydrogen which is measured by SIMS is lower than or equal to 2×10²⁰atoms/cm³, preferably lower than or equal to 5×10¹⁹ atoms/cm³, furtherpreferably lower than or equal to 1×10¹⁹ atoms/cm³, further preferablylower than or equal to 5×10¹⁸ atoms/cm³, further preferably lower thanor equal to 1×10¹⁸ atoms/cm³, further preferably lower than or equal to5×10¹⁷ atoms/cm³, and still further preferably lower than or equal to1×10¹⁶ atoms/cm³.

The first oxide semiconductor film 108 a preferably includes a regionhaving a lower hydrogen concentration than the second oxidesemiconductor film 108 b. When the first oxide semiconductor film 108 aincludes the region having a lower hydrogen concentration than thesecond oxide semiconductor film 108 b, the semiconductor device can behighly reliable.

When silicon or carbon that is one of elements belonging to Group 14 isincluded in the first oxide semiconductor film 108 a, oxygen vacancy isincreased in the first oxide semiconductor film 108 a, and the firstoxide semiconductor film 108 a becomes an n-type film. Thus, theconcentration of silicon or carbon (the concentration is measured bySIMS) in the first oxide semiconductor film 108 a or the concentrationof silicon or carbon (the concentration is measured by SIMS) in thevicinity of an interface with the first oxide semiconductor film 108 ais set to be lower than or equal to 2×10¹⁸ atoms/cm³, preferably lowerthan or equal to 2×10¹⁷ atoms/cm³.

In addition, the concentration of alkali metal or alkaline earth metalof the first oxide semiconductor film 108 a, which is measured by SIMS,is lower than or equal to 1×10¹⁸ atoms/cm³, preferably lower than orequal to 2×10¹⁶ atoms/cm³. Alkali metal and alkaline earth metal mightgenerate carriers when bonded to an oxide semiconductor, in which casethe off-state current of the transistor might be increased. Therefore,it is preferable to reduce the concentration of alkali metal or alkalineearth metal of the first oxide semiconductor film 108 a.

Furthermore, when including nitrogen, the first oxide semiconductor film108 a easily becomes n-type by generation of electrons serving ascarriers and an increase of carrier density. Thus, a transistorincluding an oxide semiconductor film which contains nitrogen is likelyto have normally-on characteristics. For this reason, nitrogen in theoxide semiconductor film is preferably reduced as much as possible; theconcentration of nitrogen which is measured by SIMS is preferably set tobe, for example, lower than or equal to 5×10¹⁸ atoms/cm³.

Each of the first oxide semiconductor film 108 a and the second oxidesemiconductor film 108 b may have a non-single-crystal structure, forexample. The non-single crystal structure includes a c-axis alignedcrystalline oxide semiconductor (CAAC-OS) described later, apolycrystalline structure, a microcrystalline structure, or an amorphousstructure, for example. Among the non-single crystal structure, theamorphous structure has the highest density of defect states, whereasCAAC-OS has the lowest density of defect states.

<<Insulating Film Functioning as Protective Insulating Film ofTransistor>>

The insulating films 114 and 116 each have a function of supplyingoxygen to the oxide semiconductor film 108. The insulating film 118 hasa function of a protective insulating film of the transistor 100. Theinsulating films 114 and 116 include oxygen. Furthermore, the insulatingfilm 114 is an insulating film capable of transmitting oxygen. Theinsulating film 114 also functions as a film which relieves damage tothe oxide semiconductor film 108 at the time of forming the insulatingfilm 116 in a later step.

A silicon oxide film, a silicon oxynitride film, or the like with athickness greater than or equal to 5 nm and less than or equal to 150nm, preferably greater than or equal to 5 nm and less than or equal to50 nm, can be used as the insulating film 114.

In addition, it is preferable that the number of defects in theinsulating film 114 be small and typically, the spin densitycorresponding to a signal that appears at g=2.001 due to a dangling bondof silicon be lower than or equal to 3×10¹⁷ spins/cm³ by electron spinresonance (ESR) measurement. This is because if the density of defectsin the insulating film 114 is high, oxygen is bonded to the defects andthe amount of oxygen that transmits the insulating film 114 isdecreased.

Note that all oxygen entering the insulating film 114 from the outsidedoes not move to the outside of the insulating film 114 and some oxygenremains in the insulating film 114. Furthermore, movement of oxygenoccurs in the insulating film 114 in some cases in such a manner thatoxygen enters the insulating film 114 and oxygen included in theinsulating film 114 moves to the outside of the insulating film 114.When an oxide insulating film capable of transmitting oxygen is formedas the insulating film 114, oxygen released from the insulating film 116provided over the insulating film 114 can be moved to the oxidesemiconductor film 108 through the insulating film 114.

Note that the insulating film 114 can be formed using an oxideinsulating film having a low density of states due to nitrogen oxide.Note that the density of states due to nitrogen oxide can be formedbetween the energy of the valence band maximum (E_(v) _(_) _(os)) andthe energy of the conduction band minimum (E_(c) _(_) _(os)) of theoxide semiconductor film. A silicon oxynitride film that releases lessnitrogen oxide, an aluminum oxynitride film that releases less nitrogenoxide, and the like can be used as the above oxide insulating film.

Note that a silicon oxynitride film that releases less nitrogen oxide isa film of which the amount of released ammonia is larger than the amountof released nitrogen oxide in TDS analysis; the amount of releasedammonia is typically greater than or equal to 1×10¹⁸/cm³ and less thanor equal to 5×10¹⁹/cm³. Note that the amount of released ammonia is theamount of ammonia released by heat treatment with which the surfacetemperature of a film becomes higher than or equal to 50° C. and lowerthan or equal to 650° C., preferably higher than or equal to 50° C. andlower than or equal to 550° C.

Nitrogen oxide (NO_(x); x is greater than 0 and less than or equal to 2,preferably greater than or equal to 1 and less than or equal to 2),typically NO₂ or NO, forms levels in the insulating film 114, forexample. The level is positioned in the energy gap of the oxidesemiconductor film 108. Therefore, when nitrogen oxide is diffused tothe interface between the insulating film 114 and the oxidesemiconductor film 108, an electron is in some cases trapped by thelevel on the insulating film 114 side. As a result, the trapped electronremains in the vicinity of the interface between the insulating film 114and the oxide semiconductor film 108; thus, the threshold voltage of thetransistor is shifted in the positive direction.

Nitrogen oxide reacts with ammonia and oxygen in heat treatment. Sincenitrogen oxide included in the insulating film 114 reacts with ammoniaincluded in the insulating film 116 in heat treatment, nitrogen oxideincluded in the insulating film 114 is reduced. Therefore, an electronis hardly trapped at the interface between the insulating film 114 andthe oxide semiconductor film 108.

By using such an oxide insulating film, the insulating film 114 canreduce the shift in the threshold voltage of the transistor, which leadsto a smaller change in the electrical characteristics of the transistor.

Note that in an ESR spectrum at 100 K or lower of the insulating film114, by heat treatment of a manufacturing process of the transistor,typically heat treatment at a temperature higher than or equal to 300°C. and lower than 350° C., a first signal that appears at a g-factor ofgreater than or equal to 2.037 and less than or equal to 2.039, a secondsignal that appears at a g-factor of greater than or equal to 2.001 andless than or equal to 2.003, and a third signal that appears at ag-factor of greater than or equal to 1.964 and less than or equal to1.966 are observed. The split width of the first and second signals andthe split width of the second and third signals that are obtained by ESRmeasurement using an X-band are each approximately 5 mT. The sum of thespin densities of the first signal that appears at a g-factor of greaterthan or equal to 2.037 and less than or equal to 2.039, the secondsignal that appears at a g-factor of greater than or equal to 2.001 andless than or equal to 2.003, and the third signal that appears at ag-factor of greater than or equal to 1.964 and less than or equal to1.966 is lower than 1×10¹⁸ spins/cm³, typically higher than or equal to1×10¹⁷ spins/cm³ and lower than 1×10¹⁸ spins/cm³.

In the ESR spectrum at 100 K or lower, the first signal that appears ata g-factor of greater than or equal to 2.037 and less than or equal to2.039, the second signal that appears at a g-factor of greater than orequal to 2.001 and less than or equal to 2.003, and the third signalthat appears at a g-factor of greater than or equal to 1.964 and lessthan or equal to 1.966 correspond to signals attributed to nitrogenoxide (NO_(x); x is greater than 0 and less than or equal to 2,preferably greater than or equal to 1 and less than or equal to 2).Typical examples of nitrogen oxide include nitrogen monoxide andnitrogen dioxide. In other words, the lower the total spin density ofthe first signal that appears at a g-factor of greater than or equal to2.037 and less than or equal to 2.039, the second signal that appears ata g-factor of greater than or equal to 2.001 and less than or equal to2.003, and the third signal that appears at a g-factor of greater thanor equal to 1.964 and less than or equal to 1.966 is, the lower thecontent of nitrogen oxide in the oxide insulating film is.

The concentration of nitrogen of the above oxide insulating filmmeasured by SIMS is lower than or equal to 6×10²⁰ atoms/cm³.

The above oxide insulating film is formed by a PECVD method at a filmsurface temperature higher than or equal to 220° C. and lower than orequal to 350° C. using silane and dinitrogen monoxide, whereby a denseand hard film can be formed.

The insulating film 116 is formed using an oxide insulating film thatcontains oxygen in excess of that in the stoichiometric composition.Part of oxygen is released by heating from the oxide insulating filmincluding oxygen in excess of that in the stoichiometric composition.The oxide insulating film including oxygen in excess of that in thestoichiometric composition is an oxide insulating film of which theamount of released oxygen converted into oxygen atoms is greater than orequal to 1.0×10¹⁹ atoms/cm³, preferably greater than or equal to3.0×10²⁰ atoms/cm³, in TDS analysis. Note that the temperature of thefilm surface in the TDS analysis is preferably higher than or equal to100° C. and lower than or equal to 700° C., or higher than or equal to100° C. and lower than or equal to 500° C.

A silicon oxide film, a silicon oxynitride film, or the like with athickness greater than or equal to 30 nm and less than or equal to 500nm, preferably greater than or equal to 50 nm and less than or equal to400 nm, can be used as the insulating film 116.

It is preferable that the number of defects in the insulating film 116be small, and typically the spin density corresponding to a signal whichappears at g=2.001 due to a dangling bond of silicon be lower than1.5×10¹⁸ spins/cm³, preferably lower than or equal to 1×10¹⁸ spins/cm³,by ESR measurement. Note that the insulating film 116 is provided moreapart from the oxide semiconductor film 108 than the insulating film 114is; thus, the insulating film 116 may have higher density of defectsthan the insulating film 114.

Furthermore, the insulating films 114 and 116 can be formed usinginsulating films formed of the same kinds of materials; thus, a boundarybetween the insulating films 114 and 116 cannot be clearly observed insome cases. Thus, in this embodiment, the boundary between theinsulating films 114 and 116 is shown by a dashed line. Although atwo-layer structure of the insulating films 114 and 116 is described inthis embodiment, the present invention is not limited to this. Forexample, a single-layer structure of the insulating film 114 may beemployed.

The insulating film 118 includes nitrogen. Alternatively, the insulatingfilm 118 includes nitrogen and silicon. The insulating film 118 has afunction of blocking oxygen, hydrogen, water, alkali metal, alkalineearth metal, or the like. It is possible to prevent outward diffusion ofoxygen from the oxide semiconductor film 108, outward diffusion ofoxygen included in the insulating films 114 and 116, and entry ofhydrogen, water, or the like into the oxide semiconductor film 108 fromthe outside by providing the insulating film 118. A nitride insulatingfilm, for example, can be used as the insulating film 118. The nitrideinsulating film is formed using silicon nitride, silicon nitride oxide,aluminum nitride, aluminum nitride oxide, or the like. Note that insteadof the nitride insulating film having a blocking effect against oxygen,hydrogen, water, alkali metal, alkaline earth metal, and the like, anoxide insulating film having a blocking effect against oxygen, hydrogen,water, and the like may be provided. As the oxide insulating film havinga blocking effect against oxygen, hydrogen, water, and the like, analuminum oxide film, an aluminum oxynitride film, a gallium oxide film,a gallium oxynitride film, an yttrium oxide film, an yttrium oxynitridefilm, a hafnium oxide film, a hafnium oxynitride film, and the like canbe given.

Although the variety of films such as the conductive films, theinsulating films, and the oxide semiconductor films which are describedabove can be formed by a sputtering method or a PECVD method, such filmsmay be formed by another method, e.g., a thermal CVD method. Examples ofthe thermal CVD method include a metal organic chemical vapor deposition(MOCVD) method and an atomic layer deposition (ALD) method.

A thermal CVD method has an advantage that no defect due to plasmadamage is generated because it does not utilize plasma for forming afilm.

Deposition by a thermal CVD method may be performed in such a mannerthat a source gas and an oxidizer are supplied to the chamber at a timeso that the pressure in a chamber is set to an atmospheric pressure or areduced pressure, and react with each other in the vicinity of thesubstrate or over the substrate.

Deposition by an ALD method may be performed in such a manner that thepressure in a chamber is set to an atmospheric pressure or a reducedpressure, source gases for reaction are sequentially introduced into thechamber, and then the sequence of the gas introduction is repeated. Forexample, two or more kinds of source gases are sequentially supplied tothe chamber by switching respective switching valves (also referred toas high-speed valves). For example, a first source gas is introduced, aninert gas (e.g., argon or nitrogen) or the like is introduced at thesame time as or after the introduction of the first source gas so thatthe source gases are not mixed, and then a second source gas isintroduced. Note that in the case where the first source gas and theinert gas are introduced at a time, the inert gas serves as a carriergas, and the inert gas may also be introduced at the same time as theintroduction of the second source gas. Alternatively, the first sourcegas may be exhausted by vacuum evacuation instead of the introduction ofthe inert gas, and then the second source gas may be introduced. Thefirst source gas is adsorbed on the surface of the substrate to form afirst layer; then the second source gas is introduced to react with thefirst layer; as a result, a second layer is stacked over the firstlayer, so that a thin film is formed. The sequence of the gasintroduction is repeated plural times until a desired thickness isobtained, whereby a thin film with excellent step coverage can beformed. The thickness of the thin film can be adjusted by the number ofrepetition times of the sequence of the gas introduction; therefore, anALD method makes it possible to accurately adjust a thickness and thusis suitable for manufacturing a minute FET.

The variety of films such as the conductive films, the insulating films,the oxide semiconductor films, and the metal oxide films in thisembodiment can be formed by a thermal CVD method such as an MOCVD methodor an ALD method. For example, in the case where an In—Ga—Zn—O film isformed, trimethylindium, trimethylgallium, and dimethylzinc are used.Note that the chemical formula of trimethylindium is In(CH₃)₃. Thechemical formula of trimethylgallium is Ga(CH₃)₃. The chemical formulaof dimethylzinc is Zn(CH₃)₂. Without limitation to the abovecombination, triethylgallium (chemical formula: Ga(C₂H₅)₃) can be usedinstead of trimethylgallium and diethylzinc (chemical formula:Zn(C₂H₅)₂) can be used instead of dimethylzinc.

For example, in the case where a hafnium oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, that is,ozone (O₃) as an oxidizer and a source gas which is obtained byvaporizing liquid containing a solvent and a hafnium precursor compound(e.g., a hafnium alkoxide or a hafnium amide such astetrakis(dimethylamide)hafnium (TDMAH)) are used. Note that the chemicalformula of tetrakis(dimethylamide)hafnium is Hf[N(CH₃)₂]₄. Examples ofanother material liquid include tetrakis(ethylmethylamide)hafnium.

For example, in the case where an aluminum oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, e.g., H₂Oas an oxidizer and a source gas which is obtained by vaporizing liquidcontaining a solvent and an aluminum precursor compound (e.g.,trimethylaluminum (TMA)) are used. Note that the chemical formula oftrimethylaluminum is Al(CH₃)₃. Examples of another material liquidinclude tris(dimethylamide)aluminum, triisobutylaluminum, and aluminumtris(2,2,6,6-tetramethyl-3,5-heptanedionate).

For example, in the case where a silicon oxide film is formed by adeposition apparatus using an ALD method, hexachlorodisilane is adsorbedon a surface where a film is to be formed, chlorine included in theadsorbate is removed, and radicals of an oxidizing gas (e.g., O₂ ordinitrogen monoxide) are supplied to react with the adsorbate.

For example, in the case where a tungsten film is formed with adeposition apparatus using an ALD method, a WF₆ gas and a B₂H₆ gas aresequentially introduced plural times to form an initial tungsten film,and then a WF₆ gas and an H₂ gas are used, so that a tungsten film isformed. Note that an SiH₄ gas may be used instead of a B₂H₆ gas.

For example, in the case where an oxide semiconductor film, e.g., anIn—Ga—Zn—O film is formed using a deposition apparatus using an ALDmethod, an In(CH₃)₃ gas and an O₃ gas are sequentially introduced pluraltimes to form an InO layer, a GaO layer is formed using a Ga(CH₃)₃ gasand an O₃ gas, and then a ZnO layer is formed using a Zn(CH₃)₂ gas andan O₃ gas. Note that the order of these layers is not limited to thisexample. A mixed compound layer such as an In—Ga—O layer, an In—Zn—Olayer, or a Ga—Zn—O layer may be formed by mixing these gases. Note thatalthough an H₂O gas which is obtained by bubbling water with an inertgas such as Ar may be used instead of an O₃ gas, it is preferable to usean O₃ gas, which does not contain H. Furthermore, instead of an In(CH₃)₃gas, an In(C₂H₅)₃ gas may be used. Instead of a Ga(CH₃)₃ gas, aGa(C₂H₅)₃ gas may be used. Furthermore, a Zn(CH₃)₂ gas may be used.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

Embodiment 8

In this embodiment, the input/output device of one embodiment of thepresent invention or structures of a transistor that can be used in theinput/output device of one embodiment of the present invention will bedescribed with reference to FIGS. 34A to 34C.

<Structure Example of Semiconductor Device>

FIG. 34A is a top view of the transistor 100. FIG. 34B is across-sectional view taken along the section line X1-X2 in FIG. 34A, andFIG. 34C is a cross-sectional view taken along the section line Y1-Y2 inFIG. 34A. Note that in FIG. 34A, some components of the transistor 100(e.g., an insulating film functioning as a gate insulating film) are notillustrated to avoid complexity. Furthermore, the direction of thesection line X1-X2 may be called a channel length direction, and thedirection of the section line Y1-Y2 may be called a channel widthdirection. As in FIG. 34A, some components are not illustrated in somecases in top views of transistors described below.

The transistor 100 can be used for the input/output device described inEmbodiment 6.

For example, when the transistor 100 is used as the transistor MD, thesubstrate 102, the conductive film 104, a stacked film of the insulatingfilms 106 and 107, the oxide semiconductor film 108, the conductive film112 a, the conductive film 112 b, a stacked film of the insulating films114 and 116, the insulating film 118, and a conductive film 120 b can bereferred to as the insulating film 701C, the conductive film 704, theinsulating film 706, the semiconductor film 708, the conductive film712A, the conductive film 712B, the insulating film 716, the insulatingfilm 721B, and the conductive film 724, respectively.

The transistor 100 includes the conductive film 104 functioning as afirst gate electrode over the substrate 102, the insulating film 106over the substrate 102 and the conductive film 104, the insulating film107 over the insulating film 106, the oxide semiconductor film 108 overthe insulating film 107, the conductive films 112 a and 112 bfunctioning as a source electrode and a drain electrode, respectively,electrically connected to the oxide semiconductor film 108, theinsulating films 114 and 116 over the oxide semiconductor film 108 andthe conductive films 112 a and 112 b, a conductive film 120 a that isover the insulating film 116 and electrically connected to theconductive film 112 b, the conductive film 120 b over the insulatingfilm 116, and the insulating film 118 over the insulating film 116 andthe conductive films 120 a and 120 b.

The insulating films 106 and 107 function as a first gate insulatingfilm of the transistor 100. The insulating films 114 and 116 function asa second gate insulating film of the transistor 100. The insulating film118 functions as a protective insulating film of the transistor 100. Inthis specification and the like, the insulating films 106 and 107 arecollectively referred to as a first insulating film, the insulatingfilms 114 and 116 are collectively referred to as a second insulatingfilm, and the insulating film 118 is referred to as a third insulatingfilm in some cases.

The conductive film 120 b can be used as a second gate electrode of thetransistor 100.

In the case where the transistor 100 is used in a pixel portion of adisplay panel, the conductive film 120 a can be used as an electrode ofa display element, or the like.

The oxide semiconductor film 108 includes the oxide semiconductor film108 b on the conductive film 104 (functioning as a first gate electrode)side, and an oxide semiconductor film 108 c over the oxide semiconductorfilm 108 b. The oxide semiconductor film 108 b and the oxidesemiconductor film 108 c contain In, M (M is Al, Ga, Y, or Sn), and Zn.

The oxide semiconductor film 108 b preferably includes a region in whichthe atomic proportion of In is larger than the atomic proportion of M,for example. The oxide semiconductor film 108 c preferably includes aregion in which the atomic proportion of In is smaller than that in theoxide semiconductor film 108 b.

The oxide semiconductor film 108 b including the region in which theatomic proportion of In is larger than that of M can increase thefield-effect mobility (also simply referred to as mobility or μFE) ofthe transistor 100. Specifically, the field-effect mobility of thetransistor 100 can exceed 10 cm²/Vs, preferably exceed 30 cm²/Vs.

For example, the use of the transistor with high field-effect mobilityfor a gate driver that generates a gate signal (specifically, ademultiplexer connected to an output terminal of a shift registerincluded in a gate driver) allows a semiconductor device or a displaydevice to have a narrow frame.

On the other hand, the oxide semiconductor film 108 b including theregion in which the atomic proportion of In is larger than that of Mmakes it easier to change electrical characteristics of the transistor100 in light irradiation. However, in the semiconductor device of oneembodiment of the present invention, the oxide semiconductor film 108 cis formed over the oxide semiconductor film 108 b. Furthermore, theoxide semiconductor film 108 c including the region in which the atomicproportion of In is smaller than that in the oxide semiconductor film108 b has larger Eg than the oxide semiconductor film 108 b. For thisreason, the oxide semiconductor film 108 which has a stacked-layerstructure of the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c has high resistance to a negative bias stresstest with light irradiation.

Impurities such as hydrogen or moisture entering the channel region ofthe oxide semiconductor film 108, particularly the oxide semiconductorfilm 108 b adversely affect the transistor characteristics and thereforecause a problem. Moreover, it is preferable that the amount ofimpurities such as hydrogen or moisture in the channel region of theoxide semiconductor film 108 b be as small as possible. Furthermore,oxygen vacancies formed in the channel region in the oxide semiconductorfilm 108 b adversely affect the transistor characteristics and thereforecause a problem. For example, oxygen vacancies formed in the channelregion in the oxide semiconductor film 108 b are bonded to hydrogen toserve as a carrier supply source. The carrier supply source generated inthe channel region in the oxide semiconductor film 108 b causes a changein the electrical characteristics, typically, a shift in the thresholdvoltage, of the transistor 100 including the oxide semiconductor film108 b. Therefore, it is preferable that the amount of oxygen vacanciesin the channel region of the oxide semiconductor film 108 b be as smallas possible.

In view of this, one embodiment of the present invention is a structurein which insulating films in contact with the oxide semiconductor film108, specifically the insulating film 107 formed under the oxidesemiconductor film 108 and the insulating films 114 and 116 formed overthe oxide semiconductor film 108 include excess oxygen. Oxygen or excessoxygen is transferred from the insulating film 107 and the insulatingfilms 114 and 116 to the oxide semiconductor film 108, whereby theoxygen vacancies in the oxide semiconductor film can be reduced. As aresult, a change in electrical characteristics of the transistor 100,particularly a change in electrical characteristics of the transistor100 due to light irradiation, can be reduced.

In one embodiment of the present invention, a manufacturing method isused in which the number of manufacturing steps is not increased or anincrease in the number of manufacturing steps is extremely small,because the insulating film 107 and the insulating films 114 and 116 aremade to contain excess oxygen. Thus, the transistors 100 can bemanufactured with high yield.

Specifically, in a step of forming the oxide semiconductor film 108 b,the oxide semiconductor film 108 b is formed by a sputtering method inan atmosphere containing an oxygen gas, whereby oxygen or excess oxygenis added to the insulating film 107 over which the oxide semiconductorfilm 108 b is formed.

Furthermore, in a step of forming the conductive films 120 a and 120 b,the conductive films 120 a and 120 b are formed by a sputtering methodin an atmosphere containing an oxygen gas, whereby oxygen or excessoxygen is added to the insulating film 116 over which the conductivefilms 120 a and 120 b are formed. Note that in some cases, oxygen orexcess oxygen is added also to the insulating film 114 and the oxidesemiconductor film 108 under the insulating film 116 when oxygen orexcess oxygen is added to the insulating film 116.

<Oxide Conductor>

Next, an oxide conductor is described. In a step of forming theconductive films 120 a and 120 b, the conductive films 120 a and 120 bserve as a protective film for suppressing release of oxygen from theinsulating films 114 and 116. The conductive films 120 a and 120 b serveas semiconductors before a step of forming the insulating film 118 andserve as conductors after the step of forming the insulating film 118.

To allow the conductive films 120 a and 120 b to serve as conductors, anoxygen vacancy is formed in the conductive films 120 a and 120 b andhydrogen is added from the insulating film 118 to the oxygen vacancy,whereby a donor level is formed in the vicinity of the conduction band.As a result, the conductivity of each of the conductive films 120 a and120 b is increased, so that the conductive films 120 a and 120 b becomeconductors. The conductive films 120 a and 120 b having becomeconductors each can be referred to as oxide conductor. Oxidesemiconductors generally have a visible light transmitting propertybecause of their large energy gap. An oxide conductor is an oxidesemiconductor having a donor level in the vicinity of the conductionband. Therefore, the influence of absorption due to the donor level issmall in an oxide conductor, and an oxide conductor has a visible lighttransmitting property comparable to that of an oxide semiconductor.

<Components of Semiconductor Device>

Components of the semiconductor device of this embodiment are describedbelow in detail.

As materials described below, materials similar to the materialsdescribed in Embodiment 7 can be used.

The material that can be used for the substrate 102 described inEmbodiment 7 can be used for the substrate 102 described in thisembodiment. Furthermore, the materials that can be used for theinsulating films 106 and 107 described in Embodiment 7 can be used forthe insulating films 106 and 107 described in this embodiment.

In addition, the materials that can be used for the conductive filmsfunctioning as the gate electrode, the source electrode, and the drainelectrode described in Embodiment 7 can be used for the conductive filmsfunctioning as the first gate electrode, the source electrode, and thedrain electrode described in this embodiment.

<<Oxide Semiconductor Film>>

The oxide semiconductor film 108 can be formed using the materialsdescribed above.

In the case where the oxide semiconductor film 108 b includes In—M—Znoxide, it is preferable that the atomic ratio of metal elements of asputtering target used for forming the In—M—Zn oxide satisfy In >M Theatomic ratio between metal elements in such a sputtering target is, forexample, In:M:Zn=2:1:3, In:M:Zn=3:1:2, or In:M:Zn=4:2:4.1.

In the case where the oxide semiconductor film 108 c is In—M—Zn oxide,it is preferable that the atomic ratio of metal elements of a sputteringtarget used for forming a film of the In—M—Zn oxide satisfy In Theatomic ratio of metal elements in such a sputtering target is, forexample, In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=1:3:2, In:M:Zn=1:3:4,or In:M:Zn=1:3:6.

In the case where the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c are formed of In—M—Zn oxide, it is preferableto use a target including polycrystalline In—M—Zn oxide as thesputtering target. The use of the target including polycrystallineIn—M—Zn oxide facilitates formation of the oxide semiconductor film 108b and the oxide semiconductor film 108 c having crystallinity. Note thatthe atomic ratios of metal elements in each of the formed oxidesemiconductor film 108 b and the formed oxide semiconductor film 108 cvary from the above atomic ratio of metal elements of the sputteringtarget within a range of ±40% as an error. For example, when asputtering target of the oxide semiconductor film 108 b with an atomicratio of In to Ga and Zn of 4:2:4.1 is used, the atomic ratio of In toGa and Zn in the oxide semiconductor film 108 b may be 4:2:3 or in thevicinity of 4:2:3.

The energy gap of the oxide semiconductor film 108 is 2 eV or more,preferably 2.5 eV or more, and further preferably 3 eV or more. The useof an oxide semiconductor having a wide energy gap can reduce off-statecurrent of the transistor 100. In particular, an oxide semiconductorfilm having an energy gap of 2 eV or more, preferably 2 eV or more and3.0 eV or less, is preferably used as the oxide semiconductor film 108b, and an oxide semiconductor film having an energy gap of 2.5 eV ormore and 3.5 eV or less is preferably used as the oxide semiconductorfilm 108 c. Furthermore, the oxide semiconductor film 108 c preferablyhas a higher energy gap than the oxide semiconductor film 108 b.

Each thickness of the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c is greater than or equal to 3 nm and less thanor equal to 200 nm, preferably greater than or equal to 3 nm and lessthan or equal to 100 nm and further preferably greater than or equal to3 nm and less than or equal to 50 nm.

An oxide semiconductor film with a low carrier density is used as theoxide semiconductor film 108 c. For example, the carrier density of theoxide semiconductor film 108 c is lower than or equal to 1×10¹⁷/cm³,preferably lower than or equal to 1×10¹⁵/cm³, further preferably lowerthan or equal to 1×10¹³/cm³, and still further preferably lower than orequal to 1×10¹¹/cm³.

Note that without limitation to the compositions and materials describedabove, a material with an appropriate composition may be used dependingon required semiconductor characteristics and electrical characteristics(e.g., field-effect mobility and threshold voltage) of a transistor.Furthermore, in order to obtain required semiconductor characteristicsof a transistor, it is preferable that the carrier density, the impurityconcentration, the defect density, the atomic ratio of a metal elementto oxygen, the interatomic distance, the density, and the like of theoxide semiconductor film 108 b and the oxide semiconductor film 108 c beset to be appropriate.

Note that it is preferable to use, as the oxide semiconductor film 108 band the oxide semiconductor film 108 c, an oxide semiconductor film inwhich the impurity concentration is low and the density of defect statesis low, in which case the transistor can have more excellent electricalcharacteristics. Here, the state in which the impurity concentration islow and the density of defect states is low (the amount of oxygenvacancy is small) is referred to as “highly purified intrinsic” or“substantially highly purified intrinsic”. A highly purified intrinsicor substantially highly purified intrinsic oxide semiconductor film hasfew carrier generation sources, and thus can have a low carrier density.Thus, a transistor in which a channel region is formed in the oxidesemiconductor film rarely has a negative threshold voltage (is rarelynormally on). A highly purified intrinsic or substantially highlypurified intrinsic oxide semiconductor film has a low density of defectstates and accordingly has a low density of trap states in some cases.Furthermore, the highly purified intrinsic or substantially highlypurified intrinsic oxide semiconductor film has an extremely lowoff-state current; even when an element has a channel width of 1×10⁶ μmand a channel length L of 10 μm, the off-state current can be less thanor equal to the measurement limit of a semiconductor parameter analyzer,that is, less than or equal to 1×10⁻¹³ A, at a voltage (drain voltage)between a source electrode and a drain electrode of from 1 V to 10 V.

Accordingly, the transistor in which the channel region is formed in thehighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film can have a small change in electricalcharacteristics and high reliability. Charges trapped by the trap statesin the oxide semiconductor film take a long time to be released and maybehave like fixed charges. Thus, the transistor whose channel region isformed in the oxide semiconductor film having a high density of trapstates has unstable electrical characteristics in some cases. Asexamples of the impurities, hydrogen, nitrogen, alkali metal, andalkaline earth metal are given.

Hydrogen included in the oxide semiconductor film reacts with oxygenbonded to a metal atom to be water, and also causes oxygen vacancy in alattice from which oxygen is released (or a portion from which oxygen isreleased). Due to entry of hydrogen into the oxygen vacancy, an electronserving as a carrier is generated in some cases. Furthermore, in somecases, bonding of part of hydrogen to oxygen bonded to a metal atomcauses generation of an electron serving as a carrier. Thus, atransistor including an oxide semiconductor film which contains hydrogenis likely to be normally on. Accordingly, it is preferable that hydrogenbe reduced as much as possible in the oxide semiconductor film 108.Specifically, in the oxide semiconductor film 108, the concentration ofhydrogen which is measured by SIMS is lower than or equal to 2×10²⁰atoms/cm³, preferably lower than or equal to 5×10¹⁹ atoms/cm³, furtherpreferably lower than or equal to 1×10¹⁹ atoms/cm³, further preferablylower than or equal to 5×10¹⁸ atoms/cm³, further preferably lower thanor equal to 1×10¹⁸ atoms/cm³, further preferably lower than or equal to5×10¹⁷ atoms/cm³, and still further preferably lower than or equal to1×10¹⁶ atoms/cm³.

The oxide semiconductor film 108 b preferably includes a region in whichhydrogen concentration is smaller than that in the oxide semiconductorfilm 108 c. A semiconductor device including the oxide semiconductorfilm 108 b having the region in which hydrogen concentration is smallerthan that in the oxide semiconductor film 108 c can be increased inreliability.

When silicon or carbon that is one of elements belonging to Group 14 isincluded in the oxide semiconductor film 108 b, oxygen vacancy increasesin the oxide semiconductor film 108 b, and the oxide semiconductor film108 b becomes an n-type film. Thus, the concentration of silicon orcarbon (the concentration is measured by SIMS) in the oxidesemiconductor film 108 b or the concentration of silicon or carbon (theconcentration is measured by SIMS) in the vicinity of an interface withthe oxide semiconductor film 108 b is set to be lower than or equal to2×10¹⁸ atoms/cm³, preferably lower than or equal to 2×10¹⁷ atoms/cm³.

In addition, the concentration of alkali metal or alkaline earth metalof the oxide semiconductor film 108 b, which is measured by SIMS, islower than or equal to 1×10¹⁸ atoms/cm³, preferably lower than or equalto 2×10¹⁶ atoms/cm³. Alkali metal and alkaline earth metal mightgenerate carriers when bonded to an oxide semiconductor, in which casethe off-state current of the transistor might be increased. Therefore,it is preferable to reduce the concentration of alkali metal or alkalineearth metal of the oxide semiconductor film 108 b.

Furthermore, when including nitrogen, the oxide semiconductor film 108 beasily becomes n-type by generation of electrons serving as carriers andan increase of carrier density.

Thus, a transistor including an oxide semiconductor film which containsnitrogen is likely to have normally-on characteristics. For this reason,nitrogen in the oxide semiconductor film is preferably reduced as muchas possible; the concentration of nitrogen which is measured by SIMS ispreferably set to be, for example, lower than or equal to 5×10¹⁸atoms/cm³.

The oxide semiconductor film 108 b and the oxide semiconductor film 108c may have a non-single-crystal structure, for example. The non-singlecrystal structure includes a c-axis aligned crystalline oxidesemiconductor (CAAC-OS) described later, a polycrystalline structure, amicrocrystalline structure, or an amorphous structure, for example.Among the non-single crystal structure, the amorphous structure has thehighest density of defect states, whereas CAAC-OS has the lowest densityof defect states.

<<Insulating Films Functioning as Second Gate Insulating Film>>

The insulating films 114 and 116 function as a second gate insulatingfilm of the transistor 100. In addition, the insulating films 114 and116 each have a function of supplying oxygen to the oxide semiconductorfilm 108. That is, the insulating films 114 and 116 contain oxygen.Furthermore, the insulating film 114 is an insulating film which cantransmit oxygen. Note that the insulating film 114 also functions as afilm which relieves damage to the oxide semiconductor film 108 at thetime of forming the insulating film 116 in a later step.

For example, the insulating films 114 and 116 described in Embodiment 7can be used as the insulating films 114 and 116 described in thisembodiment.

<<Oxide Semiconductor Film Functioning as Conductive Film, OxideSemiconductor Film Functioning as Second Gate Electrode>>

A material similar to the material of the oxide semiconductor film 108described above can be used for the conductive film 120 a functioning asa conductive film and the conductive film 120 b functioning as thesecond gate electrode.

That is, the conductive film 120 a functioning as a conductive film andthe conductive film 120 b functioning as a second gate electrode containa metal element which is the same as that contained in the oxidesemiconductor film 108 (the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c). For example, the conductive film 120 bfunctioning as a second gate electrode and the oxide semiconductor film108 (the oxide semiconductor film 108 b and the oxide semiconductor film108 c) contain the same metal element; thus, the manufacturing cost canbe reduced.

For example, in the case where the conductive film 120 a functioning asa conductive film and the conductive film 120 b functioning as a secondgate electrode are each In—M—Zn oxide, the atomic ratio of metalelements in a sputtering target used for forming the In—M—Zn oxidepreferably satisfies In≧M. The atomic ratio of metal elements in such asputtering target is In:M:Zn=2:1:3, In:M:Zn=3:1:2, In:M:Zn=4:2:4.1, orthe like.

The conductive film 120 a functioning as a conductive film and theconductive film 120 b functioning as a second gate electrode can eachhave a single-layer structure or a stacked-layer structure of two ormore layers. Note that in the case where the conductive films 120 a and120 b each have a stacked-layer structure, the composition of thesputtering target is not limited to that described above.

<<Insulating Film Functioning as Protective Insulating Film ofTransistor>>

The insulating film 118 functions as a protective insulating film of thetransistor 100.

The insulating film 118 includes one or both of hydrogen and nitrogen.Alternatively, the insulating film 118 includes nitrogen and silicon.The insulating film 118 has a function of blocking oxygen, hydrogen,water, alkali metal, alkaline earth metal, or the like. It is possibleto prevent outward diffusion of oxygen from the oxide semiconductor film108, outward diffusion of oxygen included in the insulating films 114and 116, and entry of hydrogen, water, or the like into the oxidesemiconductor film 108 from the outside by providing the insulating film118.

The insulating film 118 has a function of supplying one or both ofhydrogen and nitrogen to the conductive film 120 a functioning as aconductive film and the conductive film 120 b functioning as a secondgate electrode. The insulating film 118 preferably includes hydrogen andhas a function of supplying the hydrogen to the conductive films 120 aand 120 b. The conductive films 120 a and 120 b supplied with hydrogenfrom the insulating film 118 function as conductors.

A nitride insulating film, for example, can be used as the insulatingfilm 118. The nitride insulating film is formed using silicon nitride,silicon nitride oxide, aluminum nitride, aluminum nitride oxide, or thelike.

Although the variety of films such as the conductive films, theinsulating films, and the oxide semiconductor films which are describedabove can be formed by a sputtering method or a PECVD method, such filmsmay be formed by another method, e.g., a thermal CVD method. Examples ofthe thermal CVD method include an MOCVD method and an ALD method.

A thermal CVD method has an advantage that no defect due to plasmadamage is generated because it does not utilize plasma for forming afilm.

Deposition by a thermal CVD method may be performed in such a mannerthat a source gas and an oxidizer are supplied to the chamber at a timeso that the pressure in a chamber is set to an atmospheric pressure or areduced pressure, and react with each other in the vicinity of thesubstrate or over the substrate.

Deposition by an ALD method may be performed in such a manner that thepressure in a chamber is set to an atmospheric pressure or a reducedpressure, source gases for reaction are sequentially introduced into thechamber, and then the sequence of the gas introduction is repeated. Forexample, two or more kinds of source gases are sequentially supplied tothe chamber by switching respective switching valves (also referred toas high-speed valves). For example, a first source gas is introduced, aninert gas (e.g., argon or nitrogen) or the like is introduced at thesame time as or after the introduction of the first source gas so thatthe source gases are not mixed, and then a second source gas isintroduced. Note that in the case where the first source gas and theinert gas are introduced at a time, the inert gas serves as a carriergas, and the inert gas may also be introduced at the same time as theintroduction of the second source gas. Alternatively, the first sourcegas may be exhausted by vacuum evacuation instead of the introduction ofthe inert gas, and then the second source gas may be introduced. Thefirst source gas is adsorbed on the surface of the substrate to form afirst layer; then the second source gas is introduced to react with thefirst layer; as a result, a second layer is stacked over the firstlayer, so that a thin film is formed. The sequence of the gasintroduction is repeated plural times until a desired thickness isobtained, whereby a thin film with excellent step coverage can beformed. The thickness of the thin film can be adjusted by the number ofrepetition times of the sequence of the gas introduction; therefore, anALD method makes it possible to accurately adjust a thickness and thusis suitable for manufacturing a minute FET.

The variety of films such as the conductive films, the insulating films,the oxide semiconductor films, and the metal oxide films in thisembodiment can be formed by a thermal CVD method such as an MOCVD methodor an ALD method. For example, in the case where an In—Ga—Zn—O film isformed, trimethylindium, trimethylgallium, and dimethylzinc are used.Note that the chemical formula of trimethylindium is In(CH₃)₃. Thechemical formula of trimethylgallium is Ga(CH₃)₃. The chemical formulaof dimethylzinc is Zn(CH₃)₂. Without limitation to the abovecombination, triethylgallium (chemical formula: Ga(C₂H₅)₃) can be usedinstead of trimethylgallium and diethylzinc (chemical formula:Zn(C₂H₅)₂) can be used instead of dimethylzinc.

For example, in the case where a hafnium oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, that is,ozone (O₃) as an oxidizer and a source gas which is obtained byvaporizing liquid containing a solvent and a hafnium precursor compound(e.g., a hafnium alkoxide or a hafnium amide such astetrakis(dimethylamide)hafnium (TDMAH)) are used. Note that the chemicalformula of tetrakis(dimethylamide)hafnium is Hf[N(CH₃)₂]₄. Examples ofanother material liquid include tetrakis (ethylmethylamide)hafnium.

For example, in the case where an aluminum oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, e.g., H₂Oas an oxidizer and a source gas which is obtained by vaporizing liquidcontaining a solvent and an aluminum precursor compound (e.g.,trimethylaluminum (TMA)) are used. Note that the chemical formula oftrimethylaluminum is Al(CH₃)₃. Examples of another material liquidinclude tris(dimethylamide)aluminum, triisobutylaluminum, and aluminumtris(2,2,6,6-tetramethyl-3,5-heptanedionate).

For example, in the case where a silicon oxide film is formed by adeposition apparatus using an ALD method, hexachlorodisilane is adsorbedon a surface where a film is to be formed, chlorine included in theadsorbate is removed, and radicals of an oxidizing gas (e.g., O₂ ordinitrogen monoxide) are supplied to react with the adsorbate.

For example, in the case where a tungsten film is formed with adeposition apparatus using an ALD method, a WF₆ gas and a B₂H₆ gas aresequentially introduced plural times to form an initial tungsten film,and then a WF₆ gas and an H₂ gas are used, so that a tungsten film isformed. Note that an SiH₄ gas may be used instead of a B₂H₆ gas.

For example, in the case where an oxide semiconductor film, e.g., anIn—Ga—Zn—O film is formed using a deposition apparatus using an ALDmethod, an In(CH₃)₃ gas and an O₃ gas are sequentially introduced pluraltimes to form an InO layer, a GaO layer is formed using a Ga(CH₃)₃ gasand an O₃ gas, and then a ZnO layer is formed using a Zn(CH₃)₂ gas andan O₃ gas. Note that the order of these layers is not limited to thisexample. A mixed compound layer such as an In—Ga—O layer, an In—Zn—Olayer, or a Ga—Zn—O layer may be formed by mixing these gases. Note thatalthough an H₂O gas which is obtained by bubbling water with an inertgas such as Ar may be used instead of an O₃ gas, it is preferable to usean O₃ gas, which does not contain H. Furthermore, instead of an In(CH₃)₃gas, an In(C₂H₅)₃ gas may be used. Instead of a Ga(CH₃)₃ gas, aGa(C₂H₅)₃ gas may be used. Furthermore, a Zn(CH₃)₂ gas may be used.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

Embodiment 9

In this embodiment, the structure of a data processing device of oneembodiment of the present invention is described with reference to FIGS.35A and 35B, FIGS. 36A to 36C, FIGS. 37A and 37B, and FIG. 38.

FIG. 35A is a block diagram illustrating the structure of a dataprocessing device 200. FIG. 35B is a projection view illustrating anexample of an external view of the data processing device 200.

FIG. 36A is a diagram illustrating the structure of a display portion230. FIG. 36B is a diagram illustrating the structure of a displayportion 230B. FIG. 36C is a circuit diagram illustrating the structureof a pixel 232 (i, j).

<Structural Example of Data Processing Device>

The data processing device 200 described in this embodiment includes anarithmetic device 210 and an input/output device 220 (see FIG. 35A).

The arithmetic device 210 has a function of receiving positional data P1and supplying image data V and control data.

The input/output device 220 has a function of supplying the positionaldata P1 and receive the image data V and the control data.

The input/output device 220 includes the display portion 230 thatdisplays the image data V and an input portion 240 that supplies thepositional data P1.

The display portion 230 includes a display element and a pixel circuitfor driving the display element.

The input portion 240 has functions of sensing the position of a pointerand supplying the positional data P1 sensed in accordance with theposition.

The arithmetic device 210 is configured to determine the moving speed ofthe pointer in accordance with the positional data P1, and the like.

The arithmetic device 210 is configured to determine the contrast orbrightness of the image data V in accordance with the moving speed, andthe like.

With this structure, eyestrain on a user caused when the displayposition of image data is moved can be reduced, that is, eye-friendlydisplay can be achieved. As a result, a novel data processing devicewith high convenience or high reliability can be provided.

<Structure>

The data processing device of one embodiment of the present inventionincludes the arithmetic device 210 or the input/output device 220.

<<Arithmetic Device 210>>

The arithmetic device 210 includes an arithmetic portion 211 and amemory portion 212. The arithmetic device 210 further includes atransmission path 214 and an input/output interface 215 (see FIG. 35A).

<<Arithmetic Portion 211>>

The arithmetic portion 211 is configured to, for example, execute aprogram.

For example, a CPU described in Embodiment 10 can be used for thearithmetic portion 211. In that case, power consumption can be reduced.

<<Memory Portion 212>>

The memory portion 212 is configured to, for example, store the programexecuted by the arithmetic portion 211, initial data, setting data, animage, or the like.

Specifically, a hard disk, a flash memory, a memory including atransistor including an oxide semiconductor, or the like can be used forthe memory portion 212.

<<Input/Output Interface 215 and Transmission Path 214>>

The input/output interface 215 includes a terminal or a wiring and isconfigured to supply and receive data. For example, the input/outputinterface 215 can be electrically connected to the transmission path 214and the input/output device 220.

The transmission path 214 includes a wiring and is configured to supplyand receive data. For example, the transmission path 214 can beelectrically connected to the input/output interface 215. In addition,the transmission path 214 can be electrically connected to thearithmetic portion 211, the memory portion 212, or the input/outputinterface 215

<<Input/Output Device 220>>

The input/output device 220 includes the display portion 230, the inputportion 240, a sensor portion 250, or a communication portion 290. Forexample, the input/output device described in Embodiment 2, Embodiment4, or the like can be used as the input/output device of thisembodiment.

<<Display Portion 230>>

The display portion 230 includes a display region 231, the drivercircuit GD, and the driver circuit SD (see FIG. 36A).

The display region 231 includes a plurality of pixels 232 (i, 1) to 232(i, n) arranged in the row direction, a plurality of pixels 232 (1, j)to 232 (m, j) arranged in the column direction, the scan line G (i)electrically connected to the plurality of pixels 232 (i, 1) to 232 (i,n), the signal line S (j) electrically connected to the pixels 232 (1,j) to 232 (m, j) arranged in the column direction crossing the rowdirection. Note that i is an integer greater than or equal to 1 and lessthan or equal to m, j is an integer greater than or equal to 1 and lessthan or equal to n, and each of m and n is an integer greater than orequal to 1.

Note that the pixel 232 (i, j) is electrically connected to the scanline G1 (i), the signal line S (j), and the wiring VCOM (see FIG. 36C).

The display portion 230 can include a plurality of driver circuits. Forexample, the display portion 230B can include a driver circuit GDA and adriver circuit GDB (see FIG. 36B).

<<Driver Circuit GD>>

The driver circuit GD is configured to supply a selection signal inaccordance with the control data.

For example, the driver circuit GD is configured to supply a selectionsignal to one scan line at a frequency of 30 Hz or higher, preferably 60Hz or higher, in accordance with the control data. Accordingly, movingimages can be smoothly displayed.

For example, the driver circuit GD is configured to supply a selectionsignal to one scan line at a frequency of lower than 30 Hz, preferablylower than 1 Hz, more preferably less than once per minute, inaccordance with the control data. Accordingly, a still image can bedisplayed while flickering is suppressed.

For example, in the case where a plurality of driver circuits isprovided, the driver circuits GDA and GDB may supply the selectionsignals at different frequencies. Specifically, the selection signal canbe supplied at a higher frequency to a region on which moving images aresmoothly displayed than to a region on which a still image is displayedin a state where flickering is suppressed.

<<Driver Circuit SD>>

The driver circuit SD is configured to supply a video signal inaccordance with the image data V.

<<Pixel 232 (i, j)>>

The pixel 232 (i, j) includes a display element 235LC. The pixel 232 (i,j) further includes the pixel circuit for driving the display element235LC (see FIG. 36C).

<<Display Element 235LC>>

For example, a display element having a function of controlling lighttransmission can be used as the display element 235LC. Specifically, apolarizing plate and a liquid crystal element, a MEMS shutter displayelement, or the like can be used as the display element 235LC.

For example, a liquid crystal element that can be driven by an in-planeswitching (IPS) mode, a fringe field switching (FFS) mode, or the likecan be used for the display element.

A liquid crystal element that can be driven by any of the followingdriving methods can be used as the display element: a multi-domainvertical alignment (MVA) mode, an electrically tilted vertical alignment(EVA) mode, a patterned vertical alignment (PVA) mode, a continuouspinwheel alignment (CPA) mode, an advanced super-view (ASV) mode, apolymer sustained alignment (PSA) mode, an ultra violet inducedmulti-domain vertical alignment (UV²A) mode, a field inducedphoto-reactive alignment (FPA) mode, a transverse bend alignment (TBA)mode, and a super-fast response (SFR) mode.

Alternatively, a liquid crystal element that can be driven by any of thefollowing driving methods can be used as the display element: a twistednematic (TN) mode, a ferroelectric liquid crystal (FLC) mode, anantiferroelectric liquid crystal (AFLC) mode, an axially symmetricaligned micro-cell (ASM) mode, and an optically compensatedbirefringence (OCB) mode.

A liquid crystal element includes a layer containing a liquid crystalmaterial and an electrode which is provided so that an electric fieldfor controlling the alignment of the liquid crystal material can beapplied. For example, the orientation of the liquid crystal material canbe controlled by an electric field in a direction intersecting with thethickness direction of the layer containing a liquid crystal material(also referred to as the vertical direction).

For example, thermotropic liquid crystal, low-molecular liquid crystal,high-molecular liquid crystal, polymer dispersed liquid crystal,ferroelectric liquid crystal, anti-ferroelectric liquid crystal, or thelike can be used for the layer containing a liquid crystal material.These liquid crystal materials exhibit a cholesteric phase, a smecticphase, a cubic phase, a chiral nematic phase, an isotropic phase, or thelike depending on conditions. Alternatively, a liquid crystal materialwhich exhibits a blue phase can be used for the layer containing aliquid crystal material.

<<Pixel Circuit>>

The configuration of the pixel circuit can be designed according to thedisplay element.

For example, a pixel circuit which is electrically connected to the scanline G1 (i), the signal line S (j), and the wiring VCOM and which drivesthe display element 235LC is described (see FIG. 36C).

A switch, a capacitor, and the like can be used in the pixel circuit. Inaddition, a transistor, a diode, a resistor, a capacitor, an inductor,and the like can be used.

For example, one or a plurality of transistors can be used as a switch.Alternatively, a plurality of transistors connected in parallel, inseries, or in combination of parallel connection and series connectioncan be used as a switch.

For example, a capacitor may be formed by one electrode of the displayelement 235LC and a conductive film having a region overlapping with theone electrode.

For example, the pixel circuit includes a transistor functioning as aswitch SW, the display element 235LC, and a capacitor C. A gateelectrode of the transistor is electrically connected to the scan line G(i), and a first electrode of the transistor is electrically connectedto the signal line S (j). The one electrode of the display element 235LCis electrically connected to a second electrode of the transistor, andthe other electrode of the display element 235LC is electricallyconnected to the wiring VCOM. A first electrode of the capacitor C1 iselectrically connected to the second electrode of the transistor, and asecond electrode of the capacitor C1 is electrically connected to thewiring VCOM.

<<Transistor>>

For example, semiconductor films formed at the same step can be used fortransistors in the driver circuit and the pixel circuit.

As the transistors in the driver circuit and the pixel circuit,bottom-gate transistors, top-gate transistors, or the like can be used.

A manufacturing line for a bottom-gate transistor including amorphoussilicon as a semiconductor can be easily remodeled into a manufacturingline for a bottom-gate transistor including an oxide semiconductor as asemiconductor, for example. Furthermore, for example, a manufacturingline for a top-gate transistor including polysilicon as a semiconductorcan be easily remodeled into a manufacturing line for a top-gatetransistor including an oxide semiconductor as a semiconductor.

For example, a transistor including a semiconductor containing anelement of Group 4 can be used. Specifically, a semiconductor containingsilicon can be used for a semiconductor film. For example, singlecrystal silicon, polysilicon, microcrystalline silicon, or amorphoussilicon can be used for the semiconductor film of the transistor.

Note that the temperature for forming a transistor using polysilicon ina semiconductor is lower than the temperature for forming a transistorusing single crystal silicon in a semiconductor.

In addition, the transistor using polysilicon in a semiconductor hashigher field-effect mobility than the transistor using amorphous siliconin a semiconductor, and therefore a pixel including the transistor usingpolysilicon can have a high aperture ratio. Moreover, pixels arranged athigh resolution, a gate driver circuit, and a source driver circuit canbe formed over the same substrate. As a result, the number of componentsincluded in an electronic device can be reduced.

In addition, the transistor using polysilicon in a semiconductor hashigher reliability than the transistor using amorphous silicon in asemiconductor.

For example, a transistor including an oxide semiconductor can be used.Specifically, an oxide semiconductor containing indium or an oxidesemiconductor containing indium, gallium, and zinc can be used for asemiconductor film.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used. Specifically, a transistor that uses an oxide semiconductorfor a semiconductor film can be used.

A pixel circuit including the transistor that uses an oxidesemiconductor for the semiconductor film can hold a video signal for alonger time than a pixel circuit including the transistor that usesamorphous silicon for a semiconductor film. Specifically, the selectionsignal can be supplied at a frequency of lower than 30 Hz, preferablylower than 1 Hz, more preferably less than once per minute whileflickering is suppressed. Consequently, eyestrain on a user of the dataprocessing device can be reduced, and power consumption for driving canbe reduced.

Alternatively, for example, a transistor including a compoundsemiconductor can be used. Specifically, a semiconductor containinggallium arsenide can be used for a semiconductor film.

For example, a transistor including an organic semiconductor can beused. Specifically, an organic semiconductor containing any ofpolyacenes and graphene can be used for the semiconductor film.

<<Input Portion 240>>

Any of a variety of human interfaces or the like can be used as theinput portion 240 (see FIG. 35A).

For example, a keyboard, a mouse, a touch sensor, a microphone, acamera, or the like can be used as the input portion 240. Note that atouch sensor having a region overlapping with the display portion 230can be used. An input/output device that includes the display portion230 and a touch sensor having a region overlapping with the displayportion 230 can be referred to as a touch panel.

For example, a user can make various gestures (e.g., tap, drag, swipe,and pinch in) using his/her finger as a pointer on the touch panel.

The arithmetic device 210, for example, analyzes data on the position,track, or the like of the finger on the touch panel and determines thata specific gesture is supplied when the analysis results meetpredetermined conditions. Therefore, the user can supply a certainoperation instruction associated with a certain gesture by using thegesture.

For instance, the user can supply a “scrolling instruction” for changinga portion where image data is displayed by using a gesture of touchingand moving his/her finger on the touch panel.

<<Sensor Portion 250>>

The sensor portion 250 is configured to acquire data P2 by detecting thesurrounding state.

For example, a camera, an acceleration sensor, a direction sensor, apressure sensor, a temperature sensor, a humidity sensor, an illuminancesensor, or a global positioning system (GPS) signal receiving circuitcan be used as the sensor portion 250.

<<Communication Portion 290>>

The communication portion 290 is configured to supply and acquire datato/from a network.

<<Program>>

One embodiment of the present invention is described using a program ofone embodiment of the present invention with reference to FIGS. 37A and37B and FIG. 38.

FIG. 37A is a flow chart showing main processing of the program of oneembodiment of the present invention, and FIG. 37B is a flow chartshowing interrupt processing.

FIG. 38 schematically illustrates a method of displaying image data onthe display portion 230.

The program of one embodiment of the present invention includes thefollowing steps (see FIG. 37A).

In a first step, setting is initialized (see S1 in FIG. 37A).

For instance, predetermined image data and a second mode can be used forthe initialization.

For example, a still image can be used as the predetermined image data.Alternatively, a mode in which the selection signal is supplied at afrequency of lower than 30 Hz, preferably lower than 1 Hz, morepreferably less than once per minute can be used as the second mode.

In a second step, interrupt processing is allowed (see S2 in FIG. 37A).Note that an arithmetic device allowed to execute the interruptprocessing can perform the interrupt processing in parallel with themain processing. The arithmetic device which has returned from theinterrupt processing to the main processing can reflect the results ofthe interrupt processing in the main processing.

The arithmetic device may execute the interrupt processing when acounter has an initial value, and the counter may be set at a valueother than the initial value when the arithmetic device returns from theinterrupt processing. Thus, the interrupt processing is ready to beexecuted after the program is started up.

In a third step, image data is displayed in a mode selected in the firststep or the interrupt processing (see S3 in FIG. 37A).

For instance, predetermined image data is displayed in the second mode,in accordance with the initialization.

Specifically, the predetermined image data is displayed in a mode inwhich the selection signal is supplied to one scan line at a frequencyof lower than 30 Hz, preferably lower than 1 Hz, more preferably lessthan once per minute.

For example, the selection signal is supplied at Time T1 so that firstimage data PIC1 is displayed on the display portion 230 (see FIG. 38).At Time T2, which is, for example, one second after Time T1, theselection signal is supplied so that the predetermined image data isdisplayed.

Alternatively, in the case where a predetermined event is not suppliedin the interrupt processing, image data is displayed in the second mode.

For example, the selection signal is supplied at Time T5 so that fourthimage data PIC4 is displayed on the display portion 230. At Time T6,which is, for example, one second after Time T5, the selection signal issupplied so that the same image data is displayed. Note that the lengthof a period from Time T5 to Time T6 can be equal to that of a periodfrom Time T1 to Time T2.

For instance, in the case where the predetermined event is supplied inthe interrupt processing, predetermined image data is displayed in thefirst mode.

Specifically, in the case where an event associated with a “page turninginstruction” is supplied in the interrupt processing, image data isswitched from one to another in a mode in which the selection signal issupplied to one scan line at a frequency of 30 Hz or higher, preferably60 Hz or higher.

Alternatively, in the case where an event associated with the “scrollinginstruction” is supplied in the interrupt processing, second image dataPIC2, which includes part of the displayed first image data PIC1 and thefollowing part, is displayed in a mode in which the selection signal issupplied to one scan line at a frequency of 30 Hz or higher, preferably60 Hz or higher.

Thus, a moving image can be displayed smoothly by switching images inaccordance with the “page tuning instruction,” for example.Alternatively, a moving image in which an image is gradually moved inaccordance with the “scrolling instruction” can be displayed smoothly.

Specifically, the selection signal is supplied at Time T3 after theevent associated with the “scrolling instruction” is supplied so thatthe second image data PIC2 whose display position and the like arechanged from those of the first image data PIC1 is displayed (see FIG.38). The selection signal is supplied at Time T4 so that third imagedata PIC3 whose display position and the like are changed from those ofthe second image data PIC2 is displayed. Note that each of a period fromTime T2 to Time T3, a period from Time T3 to Time T4, and a period fromTime T4 to Time T5 is shorter than the period from Time T1 to Time T2.

In a fourth step, the next step is determined as follows: a fifth stepis selected when a termination instruction has been supplied, whereasthe third step is selected when the termination instruction has not beensupplied (see S4 in FIG. 37A).

Note that in the interrupt processing, for example, the terminationinstruction can be supplied.

In the fifth step, the program terminates (S5 in FIG. 37A).

The interrupt processing includes sixth to ninth steps described below(see FIG. 37B).

In the sixth step, the processing proceeds to the seventh step when apredetermined event has been supplied during a predetermined period,whereas the processing proceeds to the eighth step when thepredetermined event has not been supplied (see S6 in FIG. 37B).

For example, whether the predetermined event is supplied in apredetermined period or not can be a branch condition. Specifically, thepredetermined period can be longer than 0 seconds and shorter than orequal to 5 seconds, preferably shorter than or equal to 1 second,further preferably shorter than 0.5 seconds, still further preferablyshorter than or equal to 0.1 seconds.

For example, the predetermined event can include an event associatedwith the termination instruction.

In the seventh step, the mode is changed (see S7 in FIG. 37B).Specifically, the mode is changed to the second mode when the first modehas been selected, or the mode is changed to the first mode when thesecond mode has been selected.

In the eighth step, the interrupt processing terminates (see S8 in FIG.37B).

<<Predetermined Event>>

A variety of instructions can be associated with a variety of events.

The following instructions can be given as examples: “page-turninginstruction” for switching displayed image data from one to another and“scroll instruction” for moving the display position of part of imagedata and displaying another part continuing from that part.

For example, the following events can be used: events supplied using apointing device such as a mouse (e.g., “click” and “drag”) and eventssupplied to a touch panel with a finger or the like used as a pointer(e.g., “tap”, “drag” and “swipe”).

For example, the position of a slide bar pointed by a pointer, the swipespeed, and the drag speed can be used as parameters assigned to aninstruction associated with the predetermined event.

Specifically, a parameter that determines the page-turning speed or thelike can be used to execute the “page-turning instruction” and aparameter that determines the moving speed of the display position orthe like can be used to execute the “scroll instruction.”

For example, the display brightness, contrast, or saturation may bechanged in accordance with the page-turning speed and/or the scrollspeed.

Specifically, in the case where the page-turning speed and/or the scrollspeed are/is higher than the predetermined speed, the display brightnessmay be decreased in synchronization with the speed.

Alternatively, in the case where the page-turning speed and/or thescroll speed are/is higher than the predetermined speed, the contrastmay be decreased in synchronization with the speed.

For example, the speed at which user's eyes cannot follow displayedimages can be used as the predetermined speed.

The contrast can be reduced in such a manner that the gray level of abright region (with a high gray level) included in image data is broughtclose to the gray level of a dark region (with a low gray level)included in the image data.

Alternatively, the contrast can be reduced in such a manner that thegray level of the dark region included in image data is brought close tothe gray level of the bright region included in the image data.

Specifically, in the case where the page-turning speed and/or the scrollspeed are/is higher than the predetermined speed, display may beperformed such that the yellow tone is increased or the blue tone isdecreased in synchronization with the speed.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 10

In this embodiment, the structures of a data processing device and adata processing system which are embodiments of the present inventionare described with reference to FIGS. 39A and 39B and FIGS. 40A and 40B.

FIG. 39A is a block diagram illustrating the structure of a dataprocessing device 200B. FIG. 39B is a schematic view illustrating thestructure of a data processing system 6000.

FIG. 40A is a flow chart showing main processing of the program executedby the data processing device 200B of one embodiment of the presentinvention, and FIG. 40B is a flow chart showing interrupt processing.

<Structural Example of Data Processing Device>

The data processing device 200B described in this embodiment includesthe arithmetic device 210 and the input/output device 220 (see FIG.39A).

The arithmetic device 210 is configured to receive positional data P1and supply image data V.

The input/output device 220 is configured to supply the positional dataP1 and receive the image data V.

The input/output device 220 includes a display portion 230 that displaysthe image data V and an input portion 240 that supplies the positionaldata P1.

The input portion 240 is configured to sense the position of a pointerand supply the positional data P1 sensed in accordance with theposition.

In addition, the data processing device 200B has a remote accessfunction. For example, the data processing device 200B can acquire aninstruction from the communication portion 290 via the network andoperate. Specifically, the data processing device 200B is configured toacquire a photographing instruction from the communication portion 290via the network and take an image with a camera included in the sensorportion 250.

<Structure>

The data processing device of one embodiment of the present inventionincludes the arithmetic device 210 or the input/output device 220.

<<Arithmetic Device 210>>

The arithmetic device 210 includes the arithmetic portion 211 and thememory portion 212. The arithmetic device 210 further includes thetransmission path 214 and the input/output interface 215 (see FIG. 39A).

<<Arithmetic Portion 211>>

The arithmetic portion 211 is configured to, for example, execute aprogram.

For example, a CPU described in Embodiment 11 can be used for thearithmetic portion 211. In that case, power consumption can be reduced.

<<Memory Portion 212>>

The memory portion 212 has a function of, for example, storing theprogram executed by the arithmetic portion 211, initial data, settingdata, an image, or the like.

Specifically, a hard disk, a flash memory, a memory including atransistor including an oxide semiconductor, or the like can be used forthe memory portion 212.

<<Input/Output Interface 215 and Transmission Path 214>>

The input/output interface 215 includes a terminal or a wiring and isconfigured to supply and receive data. For example, the input/outputinterface 215 can be electrically connected to the transmission path 214and the input/output device 220.

The transmission path 214 includes a wiring and is configured to supplyand receive data. For example, the transmission path 214 can beelectrically connected to the input/output interface 215. In addition,the transmission path 214 can be electrically connected to thearithmetic portion 211, the memory portion 212, or the input/outputinterface 215.

<<Input/Output Device 220>>

The input/output device 220 includes the display portion 230, the inputportion 240, the sensor portion 250, or the communication portion 290.For example, the input/output device described in Embodiment 2,Embodiment 4, or the like can be used as the input/output device 220.

<<Display Portion 230>>

The display portion 230 has a function of displaying the image data V.

<<Input Portion 240>>

A human interface or the like can be used as the input portion 240 (seeFIG. 39A).

For example, a keyboard, a mouse, a touch sensor, a microphone, acamera, or the like can be used as the input portion 240.

Note that a touch sensor having a region overlapping with the displayportion 230 can be used for the input portion 240. Note that theinput/output device that includes the display portion 230 and the touchsensor having a region overlapping with the display portion 230 can bereferred to as a touch panel.

For example, a user can make various gestures (e.g., tap, drag, swipe,and pinch in) using his/her finger as a pointer on the touch sensor.

The arithmetic device 210, for example, analyzes data on the position,track, or the like of the finger on the touch panel and determines thata specific gesture is supplied when the analysis results meetpredetermined conditions. Furthermore, a certain operation instructioncan be associated with a certain gesture in advance. Thus, the user cansupply the certain operation instruction by the gesture.

For instance, the user can supply a “scrolling instruction” for changinga portion where image data is displayed by using a gesture of touchingand moving his/her finger on the touch panel.

<<Sensor Portion 250>>

The sensor portion 250 is configured to acquire data P2 by detecting thesurrounding state.

For example, a camera, an acceleration sensor, a direction sensor, apressure sensor, a temperature sensor, a humidity sensor, an illuminancesensor, or a global positioning system (GPS) signal receiving circuitcan be used as the sensor portion 250.

<<Communication Portion 290>>

The communication portion 290 is configured to supply and acquire datato/from a network or another data processing device.

<<Program>>

In this embodiment, a program structure of one embodiment of the presentinvention is described with reference to FIGS. 40A and 40B.

The program of one embodiment of the present invention can be executedby the arithmetic portion 211 and includes the following steps.

<<First Step>>

In a first step, setting is initialized (see S1 in FIG. 40A).

For example, in the case where data generated when the program has beenpreviously executed is stored, operation for erasing the data can beperformed in the initialization. In addition, operation for initializingthe value of a counter can be performed in the initialization.

<<Second Step>>

In a second step, interrupt processing is allowed (see S2 in FIG. 40A).Note that an arithmetic device allowed to execute the interruptprocessing can perform the interrupt processing in parallel with themain processing. The arithmetic device which has returned from theinterrupt processing to the main processing can reflect the results ofthe interrupt processing in the main processing.

The arithmetic device may execute the interrupt processing when acounter has an initial value, and the counter may be set at a valueother than the initial value when the arithmetic device returns from theinterrupt processing. Thus, the interrupt processing is ready to beexecuted after the program is started up.

<<Third Step>>

In a third step, the program moves to a fourth step when untransmitteddata remains, while the program moves to a fifth step when there is nountransmitted data (see S3 in FIG. 40A).

As an example, when data generated in the interrupt processing has notbeen transmitted yet, the program moves to the fourth step.

When the data generated in the interrupt processing has already beentransmitted, the program moves to the fifth step.

<<Fourth Step>>

In the fourth step, the untransmitted data is transmitted (see S4 inFIG. 40A). To improve security, encrypted data is preferablytransmitted.

For example, the untransmitted data is transmitted to a predeterminedserver connected to a network.

Thus, data indicating that predetermined operation has been performedcan be accumulated in the predetermined server.

<<Fifth Step>>

When a termination instruction is supplied in the fifth step, a sixthstep is selected, and when the termination instruction is not suppliedin the fifth step, the third step is selected (see S5 in FIG. 40A).

Note that in the interrupt processing, for example, the terminationinstruction can be supplied.

<<Sixth Step>>

The program is terminated in the sixth step (S6 in FIG. 40A). Note thatwhen the main processing is terminated, the interrupt processing is alsoterminated.

The interrupt processing includes seventh and eighth steps describedbelow (see FIG. 40B).

<<Seventh Step>>

In the seventh step, when operation which has been performed by thearithmetic portion in a predetermined period correspond to thepredetermined operation, the program moves to the eighth step, and whenthe operation which has been performed by the arithmetic portion in thepredetermined period does not correspond to the predetermined operation,the seventh step is repeated, again (see S7 in FIG. 40B).

For example, whether the predetermined event is supplied in apredetermined period or not can be a branch condition. Specifically, thepredetermined period can be longer than 0 seconds and shorter than orequal to 5 seconds, preferably shorter than or equal to 1 second,further preferably shorter than 0.5 seconds, still further preferablyshorter than or equal to 0.1 seconds. Accordingly, whether the operationcorresponding to the predetermined operation is performed in theoperation period of the interrupt processing can be monitored.

Note that the predetermined operation described below can be an objectto be monitored.

<<Eighth Step>>

In the eighth step, data is generated (S8 in FIG. 40B).

For example, data on the predetermined operation which has beenperformed by the arithmetic portion in the predetermined period can begenerated.

<<Predetermined Operation>>

For example, operation of recognizing a source of data acquired from anetwork can be included in the predetermined operation. Specifically,operation of recognizing a phone number of a caller, account data of ane-mail sender, account data of an SNS, URL address data, or the like canbe included in the predetermined operation. Furthermore, operation ofacquiring positional data of the data processing device 200B with aglobal positioning system or with remote access can be included in thepredetermined operation.

In addition, data for identifying these sources can be included in thedata generated in the eighth step.

For example, operation of applications executed by the data processingdevice 200B can be included in the predetermined operation.Specifically, an Internet browser, SNS client software, or operation ofa game and the like can be included in the predetermined operation.

For example, operation of recognizing an instruction to terminate theprogram can be included in the predetermined operation.

In such a manner, data on use states or use history of the dataprocessing device 200B of a user can be supplied to the network.

<Structure Example of Data Processing System>

The data processing system 6000 of one embodiment of the presentinvention is described with reference to FIG. 39B.

The data processing system 6000 includes the data processing device 200Bwhich supplies data and a data processing device 200C which acquires anddisplays the data (see FIG. 39B).

Note that a plurality of data processing devices 200B, each of whichsupplies identification data, can also be used, in which case, one dataprocessing device 200B is distinguished from another data processingdevice 200B, and data can be displayed on the data processing device200C while data supplied from one data processing device 200B isdistinguished from that of another data processing device 200B.

Note that the data processing system 6000 utilizes a network. Thenetwork includes an access point 6001B and an access point 6001C.Furthermore, the network has a server.

The access point 6001B is configured to receive data supplied from thedata processing device 200B. The access point 6001C is configured toreceive data supplied from the data processing device 200C.

For example, a router can be used as the access point 6001B or theaccess point 6001C.

<<Data Processing Device 200B>>

The data processing device 200B has the structure described above. Inaddition, the data processing device 200B is configured to supplypredetermined data to a predetermined server.

For example, a mobile phone or a smartphone can be used as the dataprocessing device 200B.

<<Data Processing Device 200C>>

For example, a data processing device having a structure similar to thatof the data processing device 200B can be used as the data processingdevice 200C.

Furthermore, a smart TV, a computer, a mobile phone, or a smartphone canbe used as the data processing device 200C.

For example, the data processing device 200C is configured to acquiredata from the access point 6001C and display the data.

The data processing device 200C is configured to monitor a predeterminedserver. Thus, data supplied to the predetermined server by the dataprocessing device 200B can be acquired by the data processing device200C.

For example, the predetermined server is monitored by dedicatedcommunication software, an Internet browser, an SNS or e-mail clientsoftware, or the like, whereby data can be acquired.

The acquired data can be displayed on the data processing device 200C.For example, a phone number of a caller, account data of an e-mailsender, account data of an SNS, URL address data, or the like which aresupplied from the data processing device 200B can be displayed.

Furthermore, the positional data of the data processing device 200Bacquired with a global positioning system can be plot on a map anddisplayed.

Specifically, the data can be displayed in a pop-up window.

Accordingly, the use states of the data processing device 200B can bemonitored by a user of the data processing device 200C.

For example, the user of the data processing device 200C can interceptand record the content of a call of the user of the data processingdevice 200B. Furthermore, the user of the data processing device 200Ccan remotely access the data processing device 200B and take a pictureof a use environment of the data processing device 200B with a camera.Furthermore, the user of the data processing device 200C can monitor thepositional data of the data processing device 200B.

Accordingly, for example, a person to be protected can be monitored by aprotector. Furthermore, a ward can be monitored by a guardian.Furthermore, a person under curatorship can be monitored by a curator.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 11

In this embodiment, a semiconductor device (memory device) that canretain stored data even when not powered and that has an unlimitednumber of write cycles, and a CPU including the semiconductor device isdescribed. The CPU described in this embodiment can be used for the dataprocessing device described in Embodiment 9 or 10, for example.

<<Memory Device>>

An example of a semiconductor device (memory device) that can retainstored data even when not powered and that has an unlimited number ofwrite cycles is shown in FIGS. 41A to 41C. Note that FIG. 41B is acircuit diagram of the structure in FIG. 41A.

The semiconductor device illustrated in FIGS. 41A and 41B includes atransistor 3200 using a first semiconductor material, a transistor 3300using a second semiconductor material, and a capacitor 3400.

The first and second semiconductor materials preferably have differentenergy gaps. For example, the first semiconductor material can be asemiconductor material other than an oxide semiconductor (examples ofsuch a semiconductor material include silicon (including strainedsilicon), germanium, silicon germanium, silicon carbide, galliumarsenide, aluminum gallium arsenide, indium phosphide, gallium nitride,and an organic semiconductor), and the second semiconductor material canbe an oxide semiconductor. A transistor using a material other than anoxide semiconductor, such as single crystal silicon, can operate at highspeed easily. In contrast, a transistor including an oxide semiconductorhas low off-state current.

The transistor 3300 is a transistor in which a channel is formed in asemiconductor layer including an oxide semiconductor. Since theoff-state current of the transistor 3300 is small, stored data can beretained for a long period. In other words, power consumption can besufficiently reduced because a semiconductor memory device in whichrefresh operation is unnecessary or the frequency of refresh operationis extremely low can be provided.

In FIG. 41B, a first wiring 3001 is electrically connected to a sourceelectrode of the transistor 3200. A second wiring 3002 is electricallyconnected to a drain electrode of the transistor 3200. A third wiring3003 is electrically connected to one of a source electrode and a drainelectrode of the transistor 3300. A fourth wiring 3004 is electricallyconnected to a gate electrode of the transistor 3300. A gate electrodeof the transistor 3200 and the other of the source electrode and thedrain electrode of the transistor 3300 are electrically connected to oneelectrode of the capacitor 3400. A fifth wiring 3005 is electricallyconnected to the other electrode of the capacitor 3400.

The semiconductor device in FIG. 41A has a feature that the potential ofthe gate electrode of the transistor 3200 can be retained, and thusenables writing, retaining, and reading of data as follows.

Writing and holding of data is described. First, the potential of thefourth wiring 3004 is set to a potential at which the transistor 3300 isturned on, so that the transistor 3300 is turned on. Accordingly, thepotential of the third wiring 3003 is supplied to the gate electrode ofthe transistor 3200 and the capacitor 3400. That is, a predeterminedcharge is supplied to the gate electrode of the transistor 3200(writing). Here, one of two kinds of charges providing differentpotentials (hereinafter referred to as a low-level charge and ahigh-level charge) is applied. After that, the potential of the fourthwiring 3004 is set to a potential at which the transistor 3300 is turnedoff, so that the transistor 3300 is turned off. Thus, the chargesupplied to the gate electrode of the transistor 3200 is retained(retaining).

Since the off-state current of the transistor 3300 is extremely low, thecharge of the gate electrode of the transistor 3200 is retained for along time.

Next, reading of data is described. An appropriate potential (a readingpotential) is supplied to the fifth wiring 3005 while a predeterminedpotential (a constant potential) is supplied to the first wiring 3001,whereby the potential of the second wiring 3002 varies depending on theamount of charge retained in the gate electrode of the transistor 3200.This is because in the case of using an n-channel transistor as thetransistor 3200, an apparent threshold voltage V_(th) _(_) _(H) at thetime when the high-level charge is given to the gate electrode of thetransistor 3200 is lower than an apparent threshold voltage V_(th) _(_)_(L) at the time when the low-level charge is given to the gateelectrode of the transistor 3200. Here, an apparent threshold voltagerefers to the potential of the fifth wiring 3005 that is needed to turnon the transistor 3200. Thus, the potential of the fifth wiring 3005 isset to a potential V₀ that is between V_(th) _(_) _(H) and V_(th) _(_)_(L), whereby charge supplied to the gate electrode of the transistor3200 can be determined. For example, in the case where the high-levelcharge is supplied to the gate electrode of the transistor 3200 inwriting and the potential of the fifth wiring 3005 is V₀ (>V_(th) _(_)_(H)), the transistor 3200 is turned on. In the case where the low-levelcharge is supplied to the gate electrode of the transistor 3200 inwriting, even when the potential of the fifth wiring 3005 is V₀ (<V_(th)_(_) _(L)), the transistor 3200 remains off. Thus, the data retained inthe gate electrode of the transistor 3200 can be read by determining thepotential of the second wiring 3002.

Note that in the case where memory cells are arrayed, it is necessarythat only data of a designated memory cell(s) can be read. For example,the fifth wiring 3005 of memory cells from which data is not read may besupplied with a potential at which the transistor 3200 is turned offregardless of the potential supplied to the gate electrode, that is, apotential lower than V_(th) _(_) _(H), whereby only data of a designatedmemory cell(s) can be read. Alternatively, the fifth wiring 3005 of thememory cells from which data is not read may be supplied with apotential at which the transistor 3200 is turned on regardless of thepotential supplied to the gate electrode, that is, a potential higherthan V_(th) _(_) _(L), whereby only data of a designated memory cell(s)can be read.

The semiconductor device illustrated in FIG. 41C is different from thesemiconductor device illustrated in FIG. 41A in that the transistor 3200is not provided. In this case, data writing and retaining operations canbe performed in a manner similar to those of the semiconductor deviceillustrated in FIG. 41A.

Next, reading of data of the semiconductor device illustrated in FIG.41C is described. When the transistor 3300 is turned on, the thirdwiring 3003 that is in a floating state and the capacitor 3400 areelectrically connected to each other, and the charge is redistributedbetween the third wiring 3003 and the capacitor 3400. As a result, thepotential of the third wiring 3003 is changed. The amount of change inthe potential of the third wiring 3003 varies depending on the potentialof the one electrode of the capacitor 3400 (or the charge accumulated inthe capacitor 3400).

For example, the potential of the third wiring 3003 after the chargeredistribution is (C_(B)×V_(B0)+C×V)/(C_(B)+C), where V is the potentialof the one electrode of the capacitor 3400, C is the capacitance of thecapacitor 3400, CB is the capacitance component of the third wiring3003, and V_(B0) is the potential of the third wiring 3003 before thecharge redistribution. Thus, it can be found that, assuming that thememory cell is in either of two states in which the potential of the oneelectrode of the capacitor 3400 is V₁ and V₀ (V₁>V₀), the potential ofthe third wiring 3003 in the case of retaining the potential V₁(=(C_(B)×V_(B0)+C×V₁)/(C_(B)+C)) is higher than the potential of thethird wiring 3003 in the case of retaining the potential V₀(=(C_(B)×V_(B0)+C×V₀)/(C_(B)+C)).

Then, by comparing the potential of the third wiring 3003 with apredetermined potential, data can be read.

In this case, a transistor containing the first semiconductor materialmay be used in a driver circuit for driving a memory cell, and atransistor containing the second semiconductor material may be stackedover the driver circuit as the transistor 3300.

When including a transistor in which a channel formation region isformed using an oxide semiconductor and which has an extremely smalloff-state current, the semiconductor device described in this embodimentcan retain stored data for an extremely long time. In other words,refresh operation becomes unnecessary or the frequency of the refreshoperation can be extremely low, which leads to a sufficient reduction inpower consumption. Moreover, stored data can be retained for a long timeeven when power is not supplied (note that a potential is preferablyfixed).

Furthermore, in the semiconductor device described in this embodiment,high voltage is not needed for writing data and there is no problem ofdeterioration of elements. Unlike in a conventional nonvolatile memory,for example, it is not necessary to inject and extract electrons intoand from a floating gate; thus, a problem such as deterioration of agate insulating film is not caused. That is, the semiconductor devicedescribed in this embodiment does not have a limit on the number oftimes data can be rewritten, which is a problem of a conventionalnonvolatile memory, and the reliability thereof is drastically improved.Furthermore, data is written depending on the state of the transistor(on or off), whereby high-speed operation can be easily achieved.

The above memory device can also be used in an LSI such as a digitalsignal processor (DSP), a custom LSI, or a programmable logic device(PLD) and a radio frequency identification (RF-ID) tag, in addition to acentral processing unit (CPU), for example.

<CPU>

A semiconductor device 1400 illustrated in FIG. 42 includes a CPU core1401, a power management unit 1421, and a peripheral circuit 1422. Thepower management unit 1421 includes a power controller 1402 and a powerswitch 1403. The peripheral circuit 1422 includes a cache 1404 includingcache memory, a bus interface (BUS I/F) 1405, and a debug interface(Debug I/F) 1406. The CPU core 1401 includes a data bus 1423, a controlunit 1407, a program counter (PC) 1408, a pipeline register 1409, apipeline register 1410, an arithmetic logic unit (ALU) 1411, and aregister file 1412. Data is transmitted between the CPU core 1401 andthe peripheral circuit 1422 such as the cache 1404 via the data bus1423.

The semiconductor device (cell) can be applied to many logic circuitstypified by the power controller 1402 and the control unit 1407,particularly to all logic circuits that can be constituted usingstandard cells. Accordingly, the semiconductor device 1400 can be small.The semiconductor device 1400 can have reduced power consumption. Thesemiconductor device 1400 can have a higher operating speed. Thesemiconductor device 1400 can have a smaller power supply voltagevariation.

When p-channel Si transistors and the transistor described in the aboveembodiment which includes an oxide semiconductor (preferably an oxidecontaining In, Ga, and Zn) in a channel formation region are used in thesemiconductor device (cell) and the semiconductor device (cell) isapplied to the semiconductor device 1400, the semiconductor device 1400can be small. The semiconductor device 1400 can have reduced powerconsumption. The semiconductor device 1400 can have a higher operatingspeed. Particularly when the Si transistors are only p-channel ones, themanufacturing cost can be reduced.

The control unit 1407 has functions of decoding and executinginstructions contained in a program such as inputted applications byintegrally controlling the operations of the PC 1408, the pipelineregisters 1409 and 1410, the ALU 1411, the register file 1412, the cache1404, the bus interface 1405, the debug interface 1406, and the powercontroller 1402.

The ALU 1411 has a function of performing a variety of arithmeticoperations such as four arithmetic operations and logic operations.

The cache 1404 has a function of temporarily storing frequently useddata. The PC 1408 is a register having a function of storing an addressof an instruction to be executed next. Although not illustrated in FIG.42, the cache 1404 includes a cache controller for controlling theoperation of the cache memory.

The pipeline register 1409 has a function of temporarily storinginstruction data.

The register file 1412 includes a plurality of registers including ageneral purpose register and can store data that is read from the mainmemory, data obtained as a result of arithmetic operations in the ALU1411, or the like.

The pipeline register 1410 has a function of temporarily storing dataused for arithmetic operations of the ALU 1411, data obtained as aresult of arithmetic operations of the ALU 1411, or the like.

The bus interface 1405 functions as a path for data between thesemiconductor device 1400 and devices outside the semiconductor device1400. The debug interface 1406 functions as a path of a signal forinputting an instruction to control debugging to the semiconductordevice 1400.

The power switch 1403 has a function of controlling supply of the powersupply voltage to circuits other than the power controller 1402 in thesemiconductor device 1400. These circuits belong to several differentpower domains. The power switch 1403 controls whether the power supplyvoltage is supplied to circuits in the same power domain. The powercontroller 1402 has a function of controlling the operation of the powerswitch 1403.

The semiconductor device 1400 having the above structure is capable ofperforming power gating. An example of the flow of the power gatingoperation will be described.

First, the CPU core 1401 sets the timing for stopping the supply of thepower supply voltage in a register of the power controller 1402. Next,an instruction to start power gating is sent from the CPU core 1401 tothe power controller 1402. Then, the registers and the cache 1404 in thesemiconductor device 1400 start data saving. Subsequently, the powerswitch 1403 stops the supply of the power supply voltage to the circuitsother than the power controller 1402 in the semiconductor device 1400.Then, an interrupt signal is input to the power controller 1402, therebystarting the supply of the power supply voltage to the circuits includedin the semiconductor device 1400. Note that a counter may be provided inthe power controller 1402 to be used to determine the timing of startingthe supply of the power supply voltage regardless of input of aninterrupt signal. Next, the registers and the cache 1404 start datarestoration. After that, execution of an instruction is resumed in thecontrol unit 1407.

This power gating can be performed in the entire processor or one ormore logic circuits included in the processor. The supply of power canbe stopped even for a short time. Accordingly, power consumption can bereduced at a fine granularity in space or time.

In performing power gating, data held by the CPU core 1401 or theperipheral circuit 1422 is preferably restored in a short time. In thatcase, the power can be turned on or off in a short time, and an effectof saving power becomes significant.

In order that the data held by the CPU core 1401 or the peripheralcircuit 1422 be restored in a short time, the data is preferablyrestored to a flip-flop circuit itself (referred to as a flip-flopcircuit capable of backup operation). Furthermore, the data ispreferably restored to an SRAM cell itself (referred to as an SRAM cellcapable of backup operation). The flip-flop circuit and SRAM cell whichare capable of backup operation preferably include transistors includingan oxide semiconductor (preferably an oxide containing In, Ga, and Zn)in a channel formation region. Consequently, the transistor has a lowoff-state current; thus, the flip-flop circuit and SRAM cell which arecapable of backup operation can retain data for a long time withoutpower supply. When the transistor has a high switching speed, theflip-flop circuit and SRAM cell which are capable of backup operationcan restore and return data in a short time in some cases.

An example of the flip-flop circuit capable of backup operation isdescribed with reference to FIG. 43.

A semiconductor device 1500 shown in FIG. 43 is an example of theflip-flop circuit capable of backup operation. The semiconductor device1500 includes a first memory circuit 1501, a second memory circuit 1502,a third memory circuit 1503, and a read circuit 1504. As a power supplyvoltage, a potential difference between a potential V1 and a potentialV2 is supplied to the semiconductor device 1500. One of the potential V1and the potential V2 is at a high level, and the other is at a lowlevel. An example of the structure of the semiconductor device 1500 whenthe potential V1 is at a low level and the potential V2 is at a highlevel is described below.

The first memory circuit 1501 has a function of retaining data when asignal D including the data is input in a period during which the powersupply voltage is supplied to the semiconductor device 1500. The firstmemory circuit 1501 outputs a signal Q including the retained data inthe period during which the power supply voltage is supplied to thesemiconductor device 1500. On the other hand, the first memory circuit1501 cannot retain data in a period during which the power supplyvoltage is not supplied to the semiconductor device 1500. That is, thefirst memory circuit 1501 can be referred to as a volatile memorycircuit.

The second memory circuit 1502 has a function of reading the data heldin the first memory circuit 1501 to store (or restore) it. The thirdmemory circuit 1503 has a function of reading the data held in thesecond memory circuit 1502 to store (or restore) it. The read circuit1504 has a function of reading the data held in the second memorycircuit 1502 or the third memory circuit 1503 to store (or return) it in(to) the first memory circuit 1501.

In particular, the third memory circuit 1503 has a function of readingthe data held in the second memory circuit 1502 to store (or restore) iteven in the period during which the power supply voltage is not suppliedto the semiconductor device 1500.

As shown in FIG. 43, the second memory circuit 1502 includes atransistor 1512 and a capacitor 1519. The third memory circuit 1503includes a transistor 1513, a transistor 1515, and a capacitor 1520. Theread circuit 1504 includes a transistor 1510, a transistor 1518, atransistor 1509, and a transistor 1517.

The transistor 1512 has a function of charging and discharging thecapacitor 1519 in accordance with data held in the first memory circuit1501. The transistor 1512 is desirably capable of charging anddischarging the capacitor 1519 at a high speed in accordance with dataheld in the first memory circuit 1501. Specifically, the transistor 1512desirably contains crystalline silicon (preferably polycrystallinesilicon, more preferably single crystal silicon) in a channel formationregion.

The on/off state of the transistor 1513 is determined in accordance withthe charge held in the capacitor 1519. The transistor 1515 has afunction of charging and discharging the capacitor 1520 in accordancewith the potential of a wiring 1544 when the transistor 1513 is in aconduction state. It is preferable that the off-state current of thetransistor 1515 be extremely small. Specifically, the transistor 1515desirably contains an oxide semiconductor (preferably an oxidecontaining In, Ga, and Zn) in a channel formation region.

Specific connection relations between the elements are as follows. Oneof a source and a drain of the transistor 1512 is connected to the firstmemory circuit 1501. The other of the source and the drain of thetransistor 1512 is connected to one electrode of the capacitor 1519, agate of the transistor 1513, and a gate of the transistor 1518. Theother electrode of the capacitor 1519 is connected to a wiring 1542. Oneof a source and a drain of the transistor 1513 is connected to thewiring 1544. The other of the source and the drain of the transistor1513 is connected to one of a source and a drain of the transistor 1515.The other of the source and the drain of the transistor 1515 isconnected to one electrode of the capacitor 1520 and a gate of thetransistor 1510. The other electrode of the capacitor 1520 is connectedto a wiring 1543. One of a source and a drain of the transistor 1510 isconnected to a wiring 1541. The other of the source and the drain of thetransistor 1510 is connected to one of a source and a drain of thetransistor 1518. The other of the source and the drain of the transistor1518 is connected to one of a source and a drain of the transistor 1509.The other of the source and the drain of the transistor 1509 isconnected to one of a source and a drain of the transistor 1517 and thefirst memory circuit 1501. The other of the source and the drain of thetransistor 1517 is connected to a wiring 1540. Although a gate of thetransistor 1509 is connected to a gate of the transistor 1517 in FIG.43, it is not necessarily connected to the gate of the transistor 1517.

The transistor described in the above embodiment as an example can beapplied to the transistor 1515. Because of the low off-state current ofthe transistor 1515, the semiconductor device 1500 can retain data for along time without power supply. The favorable switching characteristicsof the transistor 1515 allow the semiconductor device 1500 to performhigh-speed backup and recovery.

At least part of this embodiment can be implemented in combination withany of the other embodiments described in this specification asappropriate.

Embodiment 12

In this embodiment, electronic devices each of which include a displaydevice of one embodiment of the present invention are described withreference to FIGS. 44A to 44H.

FIGS. 44A to 44G illustrate electronic devices. These electronic devicescan include a housing 5000, a display portion 5001, a speaker 5003, anLED lamp 5004, operation keys 5005 (including a power switch or anoperation switch), a connection terminal 5006, a sensor 5007 (a sensorhaving a function of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared ray), amicrophone 5008, and the like.

FIG. 44A illustrates a mobile computer, which can include a switch 5009,an infrared port 5010, and the like in addition to the above components.FIG. 44B illustrates a portable image reproducing device provided with arecording medium (e.g., a DVD reproducing device), which can include asecond display portion 5002, a recording medium reading portion 5011,and the like in addition to the above components. FIG. 44C illustrates agoggle-type display, which can include the second display portion 5002,a support portion 5012, an earphone 5013, and the like in addition tothe above components. FIG. 44D illustrates a portable game machine,which can include the recording medium reading portion 5011 and the likein addition to the above components. FIG. 44E illustrates a digitalcamera that has a television reception function, which can include anantenna 5014, a shutter button 5015, an image receiving portion 5016,and the like in addition to the above components. FIG. 44F illustrates aportable game machine, which can include the second display portion5002, the recording medium reading portion 5011, and the like inaddition to the above components. FIG. 44G illustrates a portabletelevision receiver, which can include a charger 5017 capable oftransmitting and receiving signals, and the like in addition to theabove components.

The electronic devices in FIGS. 44A to 44G can have a variety offunctions such as a function of displaying a variety of data (e.g., astill image, a moving image, and a text image) on the display portion, atouch panel function, a function of displaying a calendar, date, time,and the like, a function of controlling processing with a variety ofsoftware (programs), a wireless communication function, a function ofbeing connected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading out a program or data stored in a recording medium anddisplaying it on the display portion. Furthermore, the electronic deviceincluding a plurality of display portions can have a function ofdisplaying image data mainly on one display portion while displayingtext data mainly on another display portion, a function of displaying athree-dimensional image by displaying images on a plurality of displayportions with a parallax taken into account, or the like. Furthermore,the electronic device including an image receiving portion can have afunction of shooting a still image, a function of shooting a movingimage, a function of automatically or manually correcting a shot image,a function of storing a shot image in a recording medium (an externalrecording medium or a recording medium incorporated in the camera), afunction of displaying a shot image on the display portion, or the like.Note that functions of the electronic devices in FIGS. 44A to 44G arenot limited thereto, and the electronic devices can have a variety offunctions.

FIG. 44H illustrates a smart watch, which includes a housing 7302, adisplay panel 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display panel 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display panel 7304 mayhave a rectangular display region. The display panel 7304 can display anicon 7305 indicating time, another icon 7306, and the like.

The smart watch in FIG. 44H can have a variety of functions such as afunction of displaying a variety of data (e.g., a still image, a movingimage, and a text image) on the display portion, a touch panel function,a function of displaying a calendar, date, time, and the like, afunction of controlling processing with a variety of software(programs), a wireless communication function, a function of beingconnected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading out a program or data stored in a recording medium anddisplaying it on the display portion.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. Note that the smart watch can be manufacturedusing a light-emitting element for the display panel 7304.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

For example, in this specification and the like, an explicit description“X and Y are connected” means that X and Y are electrically connected, Xand Y are functionally connected, and X and Y are directly connected.Accordingly, without being limited to a predetermined connectionrelationship, for example, a connection relationship shown in drawingsor texts, another connection relationship is included in the drawings orthe texts.

Here, X and Y each denote an object (e.g., a device, an element, acircuit, a wiring, an electrode, a terminal, a conductive film, or alayer).

Examples of the case where X and Y are directly connected include thecase where an element that allows an electrical connection between X andY (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) is notconnected between X and Y, and the case where X and Y are connectedwithout the element that allows the electrical connection between X andY provided therebetween.

For example, in the case where X and Y are electrically connected, oneor more elements that enable an electrical connection between X and Y(e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) can beconnected between X and Y. Note that the switch is controlled to beturned on or off. That is, the switch is conducting or not conducting(is turned on or off) to determine whether current flows therethrough ornot. Alternatively, the switch has a function of selecting and changinga current path. Note that the case where X and Y are electricallyconnected includes the case where X and Y are directly connected.

For example, in the case where X and Y are functionally connected, oneor more circuits that enable a functional connection between X and Y(e.g., a logic circuit such as an inverter, a NAND circuit, or a NORcircuit; a signal converter circuit such as a D/A converter circuit, anA/D converter circuit, or a gamma correction circuit; a potential levelconverter circuit such as a power supply circuit (e.g., a step-upcircuit or a step-down circuit) or a level shifter circuit for changingthe potential level of a signal; a voltage source; a current source; aswitching circuit; an amplifier circuit such as a circuit that canincrease signal amplitude, the amount of current, or the like, anoperational amplifier, a differential amplifier circuit, a sourcefollower circuit, and a buffer circuit; a signal generation circuit; amemory circuit; or a control circuit) can be connected between X and Y.For example, even when another circuit is interposed between X and Y, Xand Y are functionally connected if a signal output from X istransmitted to Y. Note that the case where X and Y are functionallyconnected includes the case where X and Y are directly connected and thecase where X and Y are electrically connected.

Note that in this specification and the like, an explicit description “Xand Y are electrically connected” means that X and Y are electricallyconnected (i.e., the case where X and Y are connected with anotherelement or another circuit provided therebetween), X and Y arefunctionally connected (i.e., the case where X and Y are functionallyconnected with another circuit provided therebetween), and X and Y aredirectly connected (i.e., the case where X and Y are connected withoutanother element or another circuit provided therebetween). That is, inthis specification and the like, the explicit description “X and Y areelectrically connected” is the same as the description “X and Y areconnected”.

For example, any of the following expressions can be used for the casewhere a source (or a first terminal or the like) of a transistor iselectrically connected to X through (or not through) Z1 and a drain (ora second terminal or the like) of the transistor is electricallyconnected to Y through (or not through) Z2, or the case where a source(or a first terminal or the like) of a transistor is directly connectedto one part of Z1 and another part of Z1 is directly connected to Xwhile a drain (or a second terminal or the like) of the transistor isdirectly connected to one part of Z2 and another part of Z2 is directlyconnected to Y.

Examples of the expressions include, “X, Y, a source (or a firstterminal or the like) of a transistor, and a drain (or a second terminalor the like) of the transistor are electrically connected to each other,and X, the source (or the first terminal or the like) of the transistor,the drain (or the second terminal or the like) of the transistor, and Yare electrically connected to each other in this order”, “a source (or afirst terminal or the like) of a transistor is electrically connected toX, a drain (or a second terminal or the like) of the transistor iselectrically connected to Y, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are electrically connected to each otherin this order”, and “X is electrically connected to Y through a source(or a first terminal or the like) and a drain (or a second terminal orthe like) of a transistor, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are provided to be connected in thisorder”. When the connection order in a circuit configuration is definedby an expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope.

Other examples of the expressions include, “a source (or a firstterminal or the like) of a transistor is electrically connected to Xthrough at least a first connection path, the first connection path doesnot include a second connection path, the second connection path is apath between the source (or the first terminal or the like) of thetransistor and a drain (or a second terminal or the like) of thetransistor, Z1 is on the first connection path, the drain (or the secondterminal or the like) of the transistor is electrically connected to Ythrough at least a third connection path, the third connection path doesnot include the second connection path, and Z2 is on the thirdconnection path” and “a source (or a first terminal or the like) of atransistor is electrically connected to X at least with a firstconnection path through Z1, the first connection path does not include asecond connection path, the second connection path includes a connectionpath through which the transistor is provided, a drain (or a secondterminal or the like) of the transistor is electrically connected to Yat least with a third connection path through Z2, and the thirdconnection path does not include the second connection path”. Stillanother example of the expression is “a source (or a first terminal orthe like) of a transistor is electrically connected to X through atleast Z1 on a first electrical path, the first electrical path does notinclude a second electrical path, the second electrical path is anelectrical path from the source (or the first terminal or the like) ofthe transistor to a drain (or a second terminal or the like) of thetransistor, the drain (or the second terminal or the like) of thetransistor is electrically connected to Y through at least Z2 on a thirdelectrical path, the third electrical path does not include a fourthelectrical path, and the fourth electrical path is an electrical pathfrom the drain (or the second terminal or the like) of the transistor tothe source (or the first terminal or the like) of the transistor”. Whenthe connection path in a circuit structure is defined by an expressionsimilar to the above examples, a source (or a first terminal or thelike) and a drain (or a second terminal or the like) of a transistor canbe distinguished from each other to specify the technical scope.

Note that these expressions are examples and there is no limitation onthe expressions. Here, X, Y, Z1, and Z2 each denote an object (e.g., adevice, an element, a circuit, a wiring, an electrode, a terminal, aconductive film, and a layer).

Even when independent components are electrically connected to eachother in a circuit diagram, one component has functions of a pluralityof components in some cases. For example, when part of a wiring alsofunctions as an electrode, one conductive film functions as the wiringand the electrode. Thus, “electrical connection” in this specificationincludes in its category such a case where one conductive film hasfunctions of a plurality of components.

REFERENCE NUMERALS

AF1: alignment film, AF2: alignment film, C: capacitor, C1: conductivefilm, C2: conductive film, CA: conductive film, CB: conductive film, C(g, h): conductive film, CD (g, h): conductive film, CE(g, h):conductive film, CF (g, h): conductive film, CG (g, h): conductive film,CL: control line, CL2: control line, COM: wiring, CF: coloring film,DC1: sensor circuit, DC1A: sensor circuit, DC1B: sensor circuit, DC11:sensor circuit, DC12: sensor circuit, DC13: sensor circuit, DC14: sensorcircuit, DC2: sensor circuit, DC3: sensor circuit, FPC: flexible printedcircuit board, GD: driver circuit, GDA: driver circuit, GDB: drivercircuit, LS: line, LV: line, MA: transistor, MC: transistor, MD:transistor, ME: transistor, MDB: transistor, MDC: transistor, MDE:transistor, ML1: signal line, ML2: signal line, ML3: signal line, ML4:signal line, MLS:

signal line, ML6: signal line, MLA: signal line, MLB: signal line, MLC:signal line, MLD: signal line, ML (g, h): signal line, MUX: selectioncircuit, S (j): signal line, SD: driver circuit, SW: switch, PIC1: imagedata, PIC2: image data, PIC3: image data, PIC4: image data, T(V) :period, T1: period, T2: period, V: image data, VCOM: wiring, 100:transistor, 102: substrate, 104: conductive film, 106: insulating film,107: insulating film, 108: oxide semiconductor film, 108 a: oxidesemiconductor film, 108 b: oxide semiconductor film, 108 c: oxidesemiconductor film,112 a: conductive film,112 b: conductive film, 114:insulating film, 116: insulating film, 118: insulating film, 120 a:conductive film, 120 b: conductive film, 150: transistor, 200: dataprocessing device, 200B: data processing device, 200C: data processingdevice, 210: arithmetic device, 211: arithmetic portion, 212: memoryportion, 214: transmission path, 215: input/output interface, 220:input/output device, 230: display portion, 230B: display portion, 231:display region, 232: pixel, 235LC: display element, 240: input portion,250: sensor portion, 290: communication portion, 301: shift register,302: selection circuit, 303: circuit, 312: pulse signal output circuit,316: capacitor, 318A: switch, 318B: switch, 318C: switch, 318D: switch,700: input/output device, 700C: input/output device,700D: input/outputdevice, 700E: input/output device, 700F: input/output device, 700G:input/output device, 700H: input/output device, 700T: input device,700TC: input device, 701: insulating film, 701C: insulating film, 702:pixel, 703: driver circuit, 703A: driver circuit, 703B: driver circuit,703C: driver circuit, 704: conductive film, 706: insulating film, 708:semiconductor film, 710: base, 710P: optical film, 711: wiring, 712A:conductive film, 712B: conductive film, 716: insulating film, 718:semiconductor film, 718A: region, 718B: region, 718C: region, 719:terminal, 721A: insulating film, 721B: insulating film, 724: conductivefilm, 724B: conductive film, 728: insulating film, 728A: insulatingfilm, 728B: insulating film, 730: sealant, 750: display element, 751:pixel electrode, 753: layer containing a liquid crystal material, 770:base, 770P: optical film, 771: insulating film, 775A: region, 775B:region, 1400: semiconductor device, 1401: CPU core, 1402: powercontroller, 1403: power switch, 1404: cache, 1405: bus interface, 1406:debug interface, 1407: control unit, 1408: PC, 1409: pipeline register,1410: pipeline register, 1411: ALU, 1412: register file, 1421: powermanagement unit, 1422: peripheral circuit, 1423: data bus, 1500:semiconductor device, 1501: memory circuit, 1502: memory circuit, 1503:memory circuit, 1504: circuit, 1509: transistor, 1510: transistor, 1512:transistor, 1513: transistor, 1515: transistor, 1517: transistor, 1518:transistor, 1519: capacitor, 1520: capacitor, 1540: wiring, 1541:wiring, 1542: wiring, 1543: wiring, 1544: wiring, 3001: wiring, 3002:wiring, 3003: wiring, 3004: wiring, 3005: wiring, 3200: transistor,3300: transistor, 3400: capacitor, 5000: housing, 5001: display portion,5002: display portion, 5003: speaker, 5004: LED lamp, 5005: operationkey, 5006: connection terminal, 5007: sensor, 5008: microphone, 5009:switch, 5010: infrared port, 5011: recording medium reading portion,5012: support portion, 5013: earphone, 5014: antenna, 5015: shutterbutton, 5016: image receiving portion, 5017: charger, 7302: housing,7304: display panel, 7305: icon, 7306: icon, 7311: operation button,7312: operation button, 7313: connection terminal, 7321: band, 7322:clasp.

This application is based on Japanese Patent Application serial no.2016-008612 filed with Japan Patent Office on Jan. 20, 2016, the entirecontents of which are hereby incorporated by reference.

1. An input device comprising: a first conductive film; a secondconductive film; a first signal line; and a second signal line, whereinthe second conductive film comprises a region that does not overlap withthe first conductive film, wherein the first signal line is electricallyconnected to the first conductive film, wherein the second signal lineis electrically connected to the second conductive film, wherein thefirst conductive film is configured to be capacitively coupled to anapproaching object, and wherein the second conductive film is configuredto be capacitively coupled to an approaching object.
 2. The input deviceaccording to claim 1, further comprising: a driver circuit; and a sensorcircuit, wherein the sensor circuit is electrically connected to thedriver circuit, wherein the driver circuit is configured to select thefirst signal line or the second signal line, wherein the driver circuitis configured to electrically connect the first signal line to thesensor circuit in a period during which the first signal line isselected, wherein the driver circuit is configured to electricallyconnect the second signal line to the sensor circuit in a period duringwhich the second signal line is selected, wherein the sensor circuit isconfigured to supply a search signal, wherein the first signal line isconfigured to receive the search signal, wherein the first signal lineis configured to supply a potential or a current that is changed inaccordance with the search signal and a capacitance coupled to the firstconductive film, and wherein the sensor circuit is configured to supplya sensing signal based on the potential or the current.
 3. Aninput/output device comprising: a display device; and the input deviceaccording to claim 2, wherein the input device is configured to sense anobject approaching a display surface side of the display device, whereinthe display device comprises a first pixel that comprises a regionoverlapping with the first conductive film, wherein the display devicecomprises a second pixel that comprises a region overlapping with thesecond conductive film, wherein the first pixel comprises a firstdisplay element, and wherein the second pixel comprises a second displayelement.
 4. The input/output device according to claim 3, furthercomprising a wiring, wherein the wiring is configured to supply apredetermined potential, wherein the driver circuit is configured toelectrically connect the second signal line to the wiring in the periodduring which the first signal line is selected, wherein the drivercircuit is configured to electrically connect the first signal line tothe wiring in the period during which the second signal line isselected, wherein the first display element comprises a first pixelelectrode and a layer comprising a liquid crystal material, wherein thefirst pixel electrode is disposed such that an electric field thatcontrols orientation of the liquid crystal material is formed betweenthe first conductive film and the first pixel electrode, wherein thesecond display element comprises a second pixel electrode and the layercomprising the liquid crystal material, and wherein the second pixelelectrode is disposed such that an electric field that controlsorientation of the liquid crystal material is formed between the secondconductive film and the second pixel electrode.
 5. The input deviceaccording to claim 1, further comprising: a driver circuit; and a sensorcircuit, wherein the sensor circuit is electrically connected to thedriver circuit, wherein the second conductive film is disposed such thatan electric field that is shielded by an approaching object is formedbetween the first conductive film and the second conductive film,wherein the driver circuit is configured to select the first signal lineand the second signal line, wherein the driver circuit is configured toelectrically connect the first signal line and the second signal line tothe sensor circuit in a period during which the first signal line andthe second signal line are selected, wherein the sensor circuit isconfigured to supply a search signal, wherein the first signal line isconfigured to receive the search signal, wherein the second signal lineis configured to supply a potential or a current that is changed inaccordance with the search signal and the electric field formed betweenthe first conductive film and the second conductive film, and whereinthe sensor circuit is configured to supply a sensing signal based on thepotential or the current.
 6. An input/output device comprising: adisplay device; and the input device according to claim 5, wherein theinput device is configured to sense an object approaching a displaysurface side of the display device, wherein the display device comprisesa first pixel that comprises a region overlapping with the firstconductive film, wherein the display device comprises a second pixelthat comprises a region overlapping with the second conductive film,wherein the first pixel comprises a first display element, and whereinthe second pixel comprises a second display element.
 7. The input/outputdevice according to claim 6, further comprising a wiring, wherein thewiring is configured to supply a predetermined potential, wherein thedriver circuit is configured to electrically connect another signal lineto the wiring in the period during which the first signal line and thesecond signal line are selected, wherein the driver circuit isconfigured to electrically connect the first signal line and the secondsignal line to the wiring in a period during which the other signal lineis selected, wherein the first display element comprises a first pixelelectrode and a layer comprising a liquid crystal material, wherein thefirst pixel electrode is disposed such that an electric field thatcontrols orientation of the liquid crystal material is formed betweenthe first conductive film and the first pixel electrode, wherein thesecond display element comprises a second pixel electrode and the layercomprising the liquid crystal material, and wherein the second pixelelectrode is disposed such that an electric field that controlsorientation of the liquid crystal material is formed between the secondconductive film and the second pixel electrode.
 8. A data processingdevice comprising: an arithmetic device; and the input/output deviceaccording to claim 3, wherein the arithmetic device is configured toreceive a positional data and supply image data and control data,wherein the arithmetic device is configured to determine a moving speedof a pointer in accordance with the positional data, and wherein thearithmetic device is configured to determine contrast or brightness ofthe image data in accordance with the moving speed of the pointer. 9.The data processing device according to claim 8, further comprising aninput portion, wherein the input portion comprises at least one of akeyboard, a hardware button, a pointing device, a touch sensor, anilluminance sensor, an imaging device, an audio input device, aviewpoint input device, and a posture detection device.
 10. A dataprocessing device comprising: an arithmetic device; and the input/outputdevice according to claim 6, wherein the arithmetic device is configuredto receive a positional data and supply image data and control data,wherein the arithmetic device is configured to determine a moving speedof a pointer in accordance with the positional data, and wherein thearithmetic device is configured to determine contrast or brightness ofthe image data in accordance with the moving speed of the pointer. 11.The data processing device according to claim 10, further comprising aninput portion, wherein the input portion comprises at least one of akeyboard, a hardware button, a pointing device, a touch sensor, anilluminance sensor, an imaging device, an audio input device, aviewpoint input device, and a posture detection device.